alright
chakra: is the energy that runs through out the body through the chakra circletory system it is used in every genjutsu and ninjutsu. ninjutsu and genjutsu are used by moulding chakra in a specific way the most common way to do this is through the use of handseals. chakra is often moulded into different shapes and forms this is called shape manipulation (the rasengan is the epitome of shape manipulation). chakra can also be change into elemental chakra which can be used to create/use elemental techniques, almost every one has atleast one chakra nature affinity and many have two or three of them. chakra can also be used to give taijutsu extra power, one example of this is the gentle fist
the strengths and weaknesses of elements goes:
fire>wind
water>fire
earth>water
lightning>earth
and wind>lightning
there are also other types of chakra such as senjutsu chakra which is chakra take from nature, it allows you to acess an ability called sage mode.
it also works to some extent as a persons life force and when fully depleted a person may die or be seriously injured