Nanites are microscopic machines which can enter a person's body. A nanite is built by manipulating atoms and contains gigabytes of computer memory. It is small enough to enter living cells and can be programmed to do numerous tasks.
When infused into the body of a being weather organic, inorganic or a combination of both. The most basic function that they are capable of preforming is enhancing the bodily functions of the host form they have been injected into, these range from enhancing base functions such as muscular strength as well as base regenerative abilities and acuity of sensory organs.
In more high tech applications the advanced nature of nanomachines can be used to not only enhance an organism but give them unique abilities not present in the host lifeform. These can range from wireless control of mechanical devices to even the manipulation of matter and the ambient energy around them.