What is the equivalent resistance?
Mario already answered your question, but you need a little visual aid. So, here's how you move components around. You should do this in your head, and with practice this will become natural.



As you can see, I am moving connections as if they were rubber bands. The important thing is not to cut them and to always make sure you preserve which component is attached to which node.

This is not the only way to transform that circuit: you could move R4 te other way around for example, but it pretty much shows how you can 'bend' your circuit without changing its property. 
Another way to do it, is to place your components unconnected in the way you like, and then drawing the connections between their terminals. For example, R4 here is connected between the leftmost node of R1 and the lower node of R3, so you could just place it there... It will come naturally after a while.