Some of you following this thread may ask this question: how many pairs there are , and which pairs do people trade? There is a large number of (real and conceptual) pairs (at least N*(N-1), where N is the number of tradeable currencies). If one looks at the major currencies of the western world (including Japan), there are at least 8. That makes for 56 pairs already! Not all pairs trade directly, but I can make two trades to make my own cross.
There are a number of ways I would look at currencies. One way is: if I were to be long pair A/B, one way I would think of is: I am holding risk of A and making some else hold the risk of B. Therefore, I could think of it as buying relatively lower risk and selling relatively higher risk. If I were to be right and the market realizes it, it would reduce the price of B relative to A, which makes the ratio go back to neutral.
When A/B goes up, some people may erroneously think B has weakened or A has strengthened, when it could be the opposite that took place or a combination of both (or the opposite of the latter combinations). Absolute references may not be an appropriate way to think about it.