Ability

The verb pouvoir (to be able to, can) expresses ability:

Je peux courir vite.
(I can run fast.)

Nous ne pouvons pas venir, nous sommes malades.
(We cannot come, we are sick.)

Savoir (to be able to, know how) expresses mental ability or know-how:

Je savais lire à l'âge de huit ans.
(I knew how to read at the age of eight.)

In the passé composé (perfect), savoir means to find out, to learn about something:

J'ai su hier que vous veniez.
(I learned yesterday that you were coming.)

In the conditional, savoir is used in the idiomatic expression:

Sauriez-vous me dire où se trouve le château de Versailles?
(Would you be able to tell me where the chateau of Versailles is?)

Both pouvoir and savoir are Irregular Verbs.