Here are definitions for some of the common terms:
Probate - A grant which allows a named person / people to deal with a deceased's assets. Probate is issued by HM Courts Service.
Grant of Representation - The term for the different types of grant. This includes, grant of probate (if there's a will) and grant of letters of administration (if there's no will).
Executor - The person or organisation named in a Will who is responsible for dealing with the deceased's estate.
Administrator - Administrators are responsible for dealing with a deceased's person estate where there's no Will. They do the same thing as executors.
Inheritance Tax - The tax due on a deceased's estate. Inheritance Tax is due on around 5% of probate applications, but even if there's no tax to pay, there's still a detailed tax form to fill out to get the grant.
Estate Administration - A deceased's assets, debts, life insurance, money etc, is their estate. Estate administration means sorting it all out from start to finish.
Beneficiary - A beneficiary is a person who will be receiving some of the deceased's money or assets. They may be named in the Will, or if there's no will, they may be receiving something because of intestacy.
Intestacy - If the deceased didn't leave a Will, they died intestate, and the rules of intestacy kick in. These are rules which say who the beneficiaries are.
Will - A document which sets out the deceased's wishes.