Savoir is for facts and skills, and it is the only one of the two that can take a clause. Connaître is for familiarity with people, places, and works, and always takes a direct object.
Where the choice changes the meaning
| Context | savoir | connaître |
|---|---|---|
| People | Not used with a person as its object. | Je connais Marie. |
| Places | Je sais où c'est — you know the fact. | Je connais Paris — you have been there. |
| Clauses | Je sais qu'il vient — que, si, or a question word. | Never takes a clause. |
| Skills | Elle sait nager — savoir plus an infinitive. | Not used. |
| Works | Not used with a book or a song as its object. | Je connais cette chanson. |
| In the passé composé | J'ai su — I found out. | J'ai connu — I met. |