Why is it that supergravity is an extension to general relativity? In what ways? What I have read until now says the following:
GR got itself concerned with gravity after the revolution of special relativity. Then supersymmetry was a plausible new theory and after the investment of supersymmetry in general relativity, supergravity was born. Thus, this chain tells us that Sugra is an extension of GR.
If this is right, I don't think this is the only way to explain it, is it? How can I technically understand how this is true?