One of the interesting things about probate law is its conservatism. Many of the forms and much of the terminology have remained virtually unchanged for hundreds (perhaps thousands) of years. Probate procedures arise from the need to have an orderly method of disposing of a deceased person's earthly goods to avoid, if possible, contention and sometimes bloodshed. The procedures also arise from the desire of people contemplating death, in general, to provide for survivors and distribute their property according to their own wishes, rather than those of their family and friends. This repetitious and very common need has resulted in standard procedures depending on the culture of the deceased.
To the benefit of genealogists, these probate procedures have produced a huge amount of valuable family history related information. Unfortunately, to some extent, these records appear impenetrable due to the formulaic and archaic language used in the procedures and documents. Attorneys spend much of their time in law school just learning the language of law and any genealogist that wishes to use these valuable documents, must to some extent, make some of the same effort.
Changes in the law in the United States during the past 50 years or so have dramatically changed the legal procedures for probate in many of the states and have also affected the terminology. If you were to visit a probate attorney today and discuss making a Will, you would likely become engaged in a discussion of Living Wills, Trusts and Powers of Attorney, rather than simply drafting a Will. I do not have the inclination to write a treatise on modern probate law but there are some radical changes in the terminology which I find useful to understand from the standpoint of genealogy rather than probate law as such.
First, the person making a Will is called the testator (male) or testatrix (female). When making a Will, the testator appoints someone to administer or dispose of the estate. The word "estate" refers to any property that survives the death of the testator and needs to be distributed to the heirs and assigns. An heir is a peson designated by law who is entitled to inherit property from the deceased. An "assign" is a person, possible not designated by law, who is given a specific item of property. The giving of this specific property is called a bequest.
The main function of probate procedures is to have a way to provide for the orderly transfer of titled property such as real estate but the procedures also encompass the transfer of untitled personal property.
Now, beginning in about 1964 in the United States, the American Bar Association, with others, formed the National Conference of Commissioners on Uniform State Laws or NCCUSL to draft suggested uniform laws. The idea here was to try to regularize all the differences in the probate laws and procedures that had arisen over the years between the different states in the United States and to try and curb some of the gross abuses such as outrageous billing practices by attorneys.
The Model Uniform Probate Code was promulgated in 1969 and although it was intended to apply to all 50 states, it was adopted by only sixteen states. When I attended law school beginning in 1972 in Arizona, we studied the "newly passed" Uniform Probate Code (UPC). Over the years, the remaining states have adopted portions of the Uniform Probate Code in a piecemeal fashion. So now, rather than having a somewhat uniform set of terms and procedures in the United States, we have all of the old terms and procedures in some areas and completely different terms and procedures in others. If you would like to read more, see Wikipedia:Uniform Probate Code for links to probate related articles.
One of the most obvious changes made by the UPC was to the designation of the administrator of the estate. Historically, this person (or persons) was called the Executor (Executrix) or Administrator (Administratrix) of the Will. The UPC changes that terminology to Personal Representative of the Estate. So, if you move from Arizona to California, not only does the law change, but many of the terms and definitions change also. It is this non-uniform application of probate law that makes understanding what is happening historically in any given state a challenge to genealogists. As a side note, many of the abuses addressed by the UPC are sill going strong in non-UPC states.
One result of the changes is that when I talk about probate in Arizona, a UPC state, with a person from a non-UPC state, I have to explain a whole new set of terms and procedures.
So what do I suggest? As with many areas of interest to genealogists, including not only probate, but real estate, court records, maps, and many other areas, we need to become educated in these specific areas in order to use the records and understand what we are reading and researching.