Design a Pushdown Automata, accepting either by final state or by empty stack to accept the set of all strings of 0’s and 1’s such that no prefix has more 1’s than 0’s

This is a homework question, but not graded.

I’m not looking for the answer, right now I’m just trying to understand the question. I don’t understand what sort of words would be accepted and what would be rejected. For example, I can’t understand whether the following word would be accepted:

011011 ; where 01 is prefix and 1011 is suffix

011011 ; where 011 is prefix and 011 is suffix

011011 ; where 0110 is prefix and 11 is suffix

I guess my question is this: Given a word, how do I know which part is the prefix? I don’t think I can proceed with the question unless this part is clear.

Please try to give an explanation without the actual PDA answer, I’d like to try it myself first.

Thanks!