Term insurance (or 'temporary life insurance') is insurance that pays out a lump sum if you die during a particular period of time. You choose how long you want to be covered for, for example you may want your cover to tie in with the end date of a mortgage, or when you retire. It can help make sure that your spouse and children will be financially secure if you die during the set term. If you survive to the end of the policy's term, nothing is paid out and the policy ends.
Whole of life assurance is insurance that is not limited by a set time and pays out when you die, whenever this happens. Because of this the premium you pay is usually higher than term insurance and you usually have to pay it for the rest of your life.