Chakra is basically the blood of our ninjutsu. It works almost similar in look but totally different in action. Chakra flows through our body through its own circulatory system reaching over 361 nodes where chakra interact with the spiritual energy raised in our minds. As does the brain work, telling our bodies what to do and which muscles to use in order to do such things, Chakra is essentially another part of our bodies that corresponds with our brain allowing us to perform such techniques of our times.
The combination of ones physical attributes and mental capabilities, users can create perform things such as breathing fire or creating illusions. Some advanced users of ninjutsu(the art of chakra moulding and manipulation) play the the ratios of physical and mental input in order to build stronger, more vibrant types of chakra.
To further note. Most Ninja are born with a natural affinities to one chakra nature within the five chakra natures, Fire(katon), Water(Suiton), Lightning(Raiton) Earth(Doton) And my favorite Wind(Fuuton). However they grow to be able to control other types of chakra based on how hard they get they're...ehm....weight...up?"
He chuckles a tad.