Help with Torchwood (BBC America)?

I am a recent fan of Torchwood. The eps I have seen involved Jack's brother, Spike from Buffy and then it went into Torchwood Children from Earth, it looks like after Children from Earth is over, there are no more episodes. Can someone tell me if this is a season finale or a series finale? How many seasons are there of Torchwood to begin with? Thanks for your help!!!