There are five ranks in the British peerage. In descending order, they are: Duke, Marquess, Earl, Viscount and Baron. What the British call an earl is a count in many other countries.
The female equivalencies are: Duchess, Marchioness, Countess, Viscountess and Baroness.
A baronet is not a peerage. It is an hereditary honour, though it ranks above most knighthoods.