Wills are a complex area and it is not intended to do more than skim the surface here, and there a whole books devoted to the subject. You may find it useful to look at the GenUKI advice pages at http://www.genuki.org.uk/big/EmeryPaper.html#Wills. There is also information to be found on the National Archives website. (Direct link to  very useful online Web Guide)

Prior to 1858 wills were proved in church courts. If the deceased had personal property in only one archdeaconry the will could be proved in the archdeacon's court. If the personal property was in more than on archdeaconry, but in only one diocese the will could be proved in the Bishop's Court.. If more than one diocese was involved but only one ecclesiastical province the will would be proves in the Prerogative Court of Canterbury (PCC) or the Prerogative Court of York. If both Canterbury and York were involved it would have to be proved in both. However the status of the PCC was such that many people had the will proved there - even if it could have been proved in a lower court. There were other church courts - called Peculiars - and a map showing which court operated where frequently makes little sense in terms of modern county boundaries. The PCC wills are held by the Public Records Office and over a million are indexed and can be ordered online. In addition microfilms and indexes are available at the Family Records Centre. The indexes of many of the church courts have been indexed and many are available in specialist centres - such as the Society of Genealogists Library. Many of the wills have been redistributed to the county records offices and wills from the lower church courts have been passed to HALS and are listed at on their site.

Prior to about 1750 it was usual for the will to be accompanied by an Inventory which recorded the property of the deceased. This will typically include the deceased's tool of trade - including livestock and planted crops on the farm in some cases. The household goods will also be listed - usually room by room - so one can learn something about the size of the house and how it was furnished. Again HALS holds many relating to Hertfordshire.

In 1858 the Probate Division of the High Court took over responsibility for proving wills and indexes have been printed which can be very informative in their own right - particularly for the 19th century. The indexes are available in the district probate offices and some records offices and a number of genealogy webs sits include the web index. In addition [in Beta testing form December 2014] the site probatesearch.service.gov.uk/#wills provides a simple but effective service which allows copies of the wills to be ordered online at £10 each. Wills can be extremely helpful as they can give details of several generations of the family - and my own experience is that in many cases well-to-do bachelor uncles and maiden aunts make the most useful wills in that they may well identify all their nephews and nieces.

The biggest problem with wills is that the vast majority of people (at least before the 20th century) did not leave one.

For specific information on Hertfordshire wills see Wills at Hertford, 1415-1858

Illustrative Examples

SEAR Wills at HALS - what a typical search of the indexes will turn up

Dolphin Smith 1882 - The will of a well-to-do farmer