Plain form し、plain form し, -
Usage
Mentioning two ore more similar things one after the other about the topic + to give a reason
Examples
鈴木さんはピアノも弾けるし、歌も歌えるし、ダンスもできます。
Mr Sukzuki can play the piano, sing and dance
ここは値段も安いし、魚も新しいし、よく食べにきます
The prices are low here, the fish is fresh so I often come here to eat
Good to know
On the reason part: If the conclusion is obvious it can be omitted. The last し can be replaced by から also.