my dear, without going into much mathematics and getting you confuse, a pip is the lowest price movement in the market and it is used to determine how much you have gained or lost in a trade. for instance, if you choose a lot size of 1 ( instaforex lot size) and the price moves by one in your direction means that your pip movement is 1pips and your money will be 1 lot multiplied by 1pip which gives you $1. same goes when you choose another lot size. so your gain or loss is simply the number of pips the market moves multiplied by the lot size that you have chosen