In the lore of the game we dont really know what they are made of there are a lot of speculations , but the agreed theory is that they are biomechanical bioengineered entities made of some kind of virus called technocyte. They are controled remotely by the Tenno , who where the kids of the adults passenger aboard the "zariman 10-0 ". This ship suffered a bad "space jump" and ended drifting the "void". When recovered only the kids where alive and they gained powers , which eventualy would be the foundation to control the Warframes.

There is a lot more lore about this game , For example the Orokin (the empire who made the warframes, and in which the tenno where in ) The sentients ( A group of sentient machines sent to another solar sistem to terraform for the orokins but eventualy returned and declared war to them ) And the recent factions of the game " the grineer" and the "corpus".

Quite an interesting game .