Mini and micro lots allow the investor to take a smaller position than the standard contract size. A full standard lot is 100,000 units of the base currency. A micro lot is 1,000 units of the base currency. That means it is 1/100th the size of a full lot.
If you would get $10.00 for every pip on a full lot, then you will get $0.10 for every pip on a micro lot. Beginners are often encouraged to trade using only micro lots because the repurcussions are minimal, but functionality is the same.
When you place a trade, you can choose how many lots you want to buy or sell. In MetaTrader, you'll open the "New Order" window and enter the lot size as "Volume" (like in the picture to the right.) You can trade any combination of full, mini, or micro lots at the same time. If you enter 1.36 for "Volume," then you are trading 1 full lot, 3 mini lots, and 6 micro lots.