What kind of cactus is this? (pic included)?

Question

http://i38.tinypic.com/xeo6fm.jpg

i just got it a few weeks ago and hes turning a little brownish yellow at the base. is that normal? what does it mean? ALSO how can i tell when theyre all dried out? are these three little stubby things usually considered one big cactus? or just 3 little ones? PLEASE ANSWER ALL OF THESE QUESTIONS OR AT LEAST TRY. i know, im sorry i have a lot of questions. i just want to know bc my last cactus rotted. and i dont want over water this time

Answer 1

you only need water every 3 months,and then only a tiny amount,and it need light place on a bright windowsill,they are slow growers and will shrivell up and go brown when dead