No, not probation. You get out of probation alive, while once you - or more accurately your estate - (because you are in no position to comment!) is in probate, things are settled for good.
We are talking about this process from a genealogical point of view, not a legal discourse. Any legal professionals reading this please cut me some slack, as this is meant to be a very short overview for genealogical purposes.
So what is probate? Probate is the legal process of inventorying, evaluating, distributing and settling a dead person's estate. This can be both real estate and one's personal estate or personal property. Land and houses are real estate, while jewelry, letters, books, pictures, artworks, clothes, stocks and bonds, etc. are personal estate.
Some places in the U. S. will have any such property pass automatically to a spouse or children; in some cases, this does not happen. What a probate court, often called a surrogate's court in the U. S. does is to make sure that such real estate and personal estate are distributed according to the deceased's last wishes (by a will for example), and according to the laws of the state that has jurisdiction.
To make it short, an executor, or an administrator if there is an estate without a valid will, is the person who coordinates the different parts of the estate for the judge and court to make a ruling and settlement. Again, leaving a great deal of legal explanation out of this discussion, the executor must pay all just and due bills that the decedent had; inventory and account for the deceased's property; and distribute the assets as per the deceased's wishes and give a report to the court. People can – and do – contest wills and decisions, but that's grist for another mill.
With that extraordinarily brief overview, we move to the questions of why this is significant for genealogy. Let me enumerate a few reasons.
1. The petition to "prove" the will in the court should contain the dead person's name and residence at the time of their decease. It should also give the date and often the place of their death. If there is not a will, there is a different format to be followed, but the petition should state whether or not a will exists and is being offered.
2. The name and the relationship of the petitioner – who may or may not be the named executor – are given.
3. The petition to probate the will, filed with the court, lists those people who are close relatives, devisees and legatees. Those ten-dollar words mean the people who have a bequeathed interest (devised to them) or a legacy given to them. It also lists those who are blood relatives generally within the limits of inheritance. This means when John Smith's will is probated, the petition lists Mary Smith, wife; Joe Smith, son; Angie Smith adopted step-daughter (catch that one?); the husband Jeff Jones of my niece Bertha Jones; cousin Frank Smith, and so on. As you can see, the statements of who is alive and what their relation was to the decedent are invaluable. One has to bear in mind that sometimes terms were used in olden days that mean different things than they do in the present.
4. The petition gives the addresses where people are living at that time. Why is this important? It should be obvious, but here's an example: I had three brothers immigrate from Germany in the 1870's. Two liked it here and stayed, while one returned after a couple years and lived out his life back overseas. But all three bought property jointly in this town, and guess what happened? The two who wanted to sell it years later had a deceased brother who was overseas. They could not give a clear title to the land unless the third brother's rights were extinguished and satisfied. What they did was easy because they had kept in touch - they contacted his children and had them all sign off their residual interest. Fine so far. When I found the 1905 will from Germany filed in my town in the U. S., it gave his children, their addresses in Germany at that time, their relation and names – and when I asked an 80 year-old German relative about these people, she had known them all personally and was able to fill me in on all of their life stories!
Another example is an old 1838 will which stated "my son John Jones and his family now residing in Birmingham, Alabama," which gave the proof that the people in Alabama who thought that they were related to a local man indeed were, since the father's will specifically stated where his children – including married daughters and their husband's names – were living.
5. The ages of any heirs who were legal minors (not of adult age) may be given as well as who is being appointed to act in their interest.
6. The inventory of goods can also be useful. Modern estates often have the financial information blocked from casual view, but older estates from before World War I usually have the bank accounts, where they were, how much was in them, any real estate owned, etc. I found a list of a farmer ancestor's property from 1892 and used it in a publication I wrote 15 years ago to show what an average farmer would have owned and what it was worth.
7. The will should obviously give the statement of the decedents' wishes, but the petition should say when and where the person died. If they died away from the usual homestead, then this could be a clue for an unnatural death, war casualty, etc.
8. The inventory of property can lead the searcher to real estate records – and thence, to other records kept in a county clerk's office.
Where can you find them?
The wills and other papers are generally filed in a probate or surrogate's court at the county level. This may vary, but remember also that as new counties were set off from old ones, that wills may be located in the parent county. If a county started in 1789, was divided in 1808, and further divided in 1821, you may have to look in three county seats. Even though the family lived in the same house all those years- the borders around them changed.
If you get copies, ask if you can take a digital photo. You may be able to enhance a digital copy that is in rough condition. As well, your ancestor signed the document! Now you have a photo of their signature.
How to cite.
Check the standard sources for citing genealogical sources, whether on film or the actual records. Richard Lackey and Elizabeth Shown Mills have written wonderful books on citing your sources.
I know of at least one commercial site that has compiled lists of wills and proceedings filed in the surrogate's court for my county, and the heir list goes far past the old compiled lists that the library has. They want you to pay for the copies, of course, but you can tell at a glance from these sites as to whether a county has records on file. My own local county does not have a surrogate's court presence online yet.