Einstein developed general relativity, which describes the gravitational field, with the mathematical idea that there was no difference in the mathematics, between the role played by the gravitational field, symbolized by
g
uv
and the metric tensor defining the geometry of space-time. Without the
gravitational field, space-time would not exist. That being the case, whenever
we ask how space-time gets to be curved by matter, we are simply asking the
equivalent question 'how does the gravitational field change?'. The
mathematics provide us with the framework we need to interpret questions such
as 'what does it mean for space-time to be curved?' by letting us rephrase
the question in terms of our old friend the gravitational field. Presumably, a
body produces a gravitational field the same way that other bodies produce the
other fundamental forces, however, we have no experimental proof that a quantum
description for the gravitational field is a reachable goal anytime soon.