Bond or Term accounts require you to tie up your money for a fixed period of time (the 'term'). Often there is no access to your money before the term is up.
These type of accounts tend to pay more competitive rates as they require your investment to be tied up for a specific period of time and withdrawals before the maturity date are often not permitted. If withdrawals are permitted without notice there will sometimes be penalty charges.
The interest rate is often fixed and the minimum investment is generally £1000 or more.