Subwoofer question

Heh guys, i am the new in the audio section. Can i ask some question here?...because i cant find where to post new thread. Recently i am planning to buy the subwoofer for my home audio system. Since my last time home audio speaker has already spoil or cant function anymore. Recently i also doing many research online to find more info about the speaker. I have a question, can i just buy the subwoofer as my home audio system?...i mean i am not going to buy other speaker just buy the subwoofer to replace my all speaker. Did this will affect the quality of the sound produce by the speaker?.....Did home audio system must contain the normal speaker(non low pitch speaker)?