's - is or has

In spoken English the words is and has are sometimes contracted to 's.

Have a look at the following examples:
1) He's listening to music. -> He is listening to music.
2) He's listened to music. -> He has listened to music.

In sentence 1) the 's is followed by listening. This verb has the ending -ing. It is Present Progressive (is + infinitive + -ing).

In sentence 2) the 's is followed by listened. This verb has the ending -ed. It is Present Perfect (regular: has + infinitive + -ed or
irregular: has + 3rd column of the irregular verbs).

The verb following the 's tells you whether it's is or has.