Let's see it with a couple of examples:

1) Someone asks you if you are done with your homework and you did 90%, so you answer that you are not done yet, but you are close. 

2) Someone asks you if you are done with your homework and you did 50%, so you answer that you are not done yet, and "you are not even close" to finish it. 

Adding on to what Alvaro wrote:

"not even close to" - the "to" generally begins a phrase that may implied rather than being explicitly stated. By that I mean, rather than saying, "I'm not even close to being finished", one might shorten it to just, "Not even close."

Basically "close" is a relationship word. That is, it is an indication of how words, concepts, statements, etc. are related to each other? For example, generally speaking, philosophy and food are not obviously related. So, if one asked me whether I am not a vegan for nutritional reasons, but I'm actually simply a meat addict, I might reply, "Not even close."