My seeds in bittorrent keep decreasing ?

Hi !~

Last night i download GTA IV torrent in the piratebay . So it took me a few hours to download and i'm done so i thought i can play it already but it said"Seeding" and my seeds keep decreasing , i'm using BitTorrent . And what seeding mean ? How long will it Seeding ?
INFO :
The file size was 3.98GB and my seeds now 200+ and keep decreasing again ~ Thanks !!
Now it increase !!!! CAN I STOP IT WITHOUT DELETING THE GAME I DOWNLOADED !