The question is broad and can hardly be fully answered in a single post. I will be very brief hoping it will help you and push you to seek for more knowledge.
Humans, like all other animals (or almost all) are chemo-organotroph. This mean we get our energy from the food we eat and we release this energy through oxydation. It is therefore chemical energy that we're using. We are then storing this energy into another chemical called ATP. Note that not only humans use ATP but any living thing on earth uses ATP (or GTP I think). ATP is then used (ATP loses one phosphate group and becomes ADP) to perform specific action (such as the use of a trans-membrane pump or the contraction of a muscle fiber).
You should have a look at wikipedia > Primary nutritional groups as well as wikipedia > chemotrophs and eventually this post.
For more information, please consider having a look at wikipedia and if you can't find feel free to ask your question in a new post. Always attempt to narrow your post down to a single, clearly defined question.