Trading pairs are the two different types of currency that are being traded against each other. You can only trade in crypto pairs like BTC. However, ETH is by far the best trading pair for most currencies because of the speed of getting funds in and out. LTC is even better if you are on an exchange that has a lot of LTS pairs.
I have always been impressed by the growth of the coins like Eth and Bitcoin. They both are extraordinary and this is what we all have witnessed in the journey so far. In addition, long term investments always pay off.