You can get so much from a single line of text. First, there's the excitement of finally tracking down your ancestor. You can discover basic details about them, as well as attach the official record to their entry in your family tree.
You can discover their age at the time of death (but remember, this may not be 100% accurate, as the person who gives that information may not be a close relative). You can also find out where the death was registered (this may not necessarily be where your ancestor was living at the time - as people can die at any time, in any place).
Sample records: [+] Click to magnify
A brief history of the Death Indexes
The formal registration of deaths in England and Wales began on 1st July 1837 with the introduction of Civil Registration. Before this, each individual parish was responsible for maintaining their own Parish register - so for events before 1837, check our Parish Records.
While Civil Registration was meant to bring all deaths together in one place, it's important to know that registration was only made compulsory by law in 1875. So if you can't find your pre-1875 ancestors here, this could be why.