There are two types of limits, from the left and from the right. take your finger and trace the graph starting at x=0 until you get to where x=1. That is the limit from the lft. Then put your finger around where x=2 and go towards where x=1 again, coming from the right to get the limit from the right. If they are different like they are for x=1, then the limit does not exist. If they are the same then the value where your finger is the value of the limit.

For example 3 there is no limit from the right because there is nothing to the right at all, but the limit is where your finger is, not where the actual point is.

That help at all?