The Knife in Counter-Strike: Global Offensive, is the only melee weapon in the game. It is also the only weapon that you cannot drop and if you do not have any guns, you will be left with the knife. It has two forms of attacks, the primary and the seconday. The primary attack is a low damage slash which is quick to execute (mouse 1). The secondary attack is a heavy damage slash, if done right can kill an enemy in 2 hits from the front, or 1 hit from the back (mouse 2). The downside is that this attack is not as quick and if you miss it takes a long time to recover.
Both teams have the knife and their only difference is in the appearance of the knife.