who

what

Used to ask about a thing, or to mean the thing that.

which

Used to ask or say which one thing from a known group you mean.

he

Stands for a man or boy already mentioned, when he is the subject of the sentence.

she

The word you use to talk about a woman or girl already mentioned.

that

Points to a person or thing further away, or the one already mentioned, and can also join two parts of a sentence.