Default [Q] battery circle widget?

hi i am new to android came from a blackberry and wanted to know does this crcle widget which appears on the left of the screen take alot of extra battery...

i have been folowing the updates i have been reading about on here now have KES7 running has improved my battery life as android os is running now at 21%?? is that still high??

sorry for being thick what does rooting mean and do????