A fixed rate stays the same for a set term, from six months to five years. You know your repayments, but extra repayments are limited and leaving early can trigger a break cost.
A floating rate moves with the market. It's usually higher than fixed rates, but you can repay as much as you like, whenever you like.
Many borrowers split the loan: most of it fixed across two or three terms so it doesn't all reprice at once, and a smaller floating or revolving-credit part for extra repayments. An offset account, where your savings reduce the interest charged, is another way to keep money working against the loan.