As the name implies, a hand is considered "Two Pair" if you can find two different pairs of different matching values. For example, if you are holding two eights and two fives, then your hand would be considered "Two Pair". The hand below is another example:
This hand has a pair of eights and a pair of fives, so it is a nice example of "Two Pair". However, note that if you had four or five of the same card you would NOT have "two pairs" in your hand since they are not two different pair values.
For this reason, you'll want to implement the Four of a Kind and the Five of a Kind methods when implementing this one to have them available as helpers.