- The image illustrates the curvature vastly exaggerated with a 2-dimensional surface and
the Earth as the
mass-energy clump causing
curvature.
It's easy to understand curved 2-dimensional spaces like the surface of a sphere. The curvature is really in 3-dimensions which very hard for humans to visualize though mathematically it can be treated.

- The spacetime
curvature is the cause of gravity
which in turn is one of the causes of the motion
of mass-energy.
So GR is
essentially a theory of gravity.
- Mass-energy is
the jargon term
in
Relativityspeak
for mass and
energy which in
relativistic physics are
the same thing, just with different emphasis as we know from
E=mc**2.
- It's all rather complicated to solve problems with
GR
since mass-energy
causes gravity and
gravity is one of the causes
of the motion of mass-energy---so there
are complicated feedback.
One has to find a self-consistent GR solutions for physical systems dominated by gravity. This is

**NOT**easy and, except for a few simple cases, requires masssive numerical solutions on the computer. - There are a small set of
exact analytic solutions
in general relativity: only 6 depending on how you count them
(see
Wikipedia: Exact solutions in general relativity;
Malcolm A. H. McCallum,
2013, Exact solutions of Einstein's equations).

Caption: Einstein's
general relativity (GR) shows that
mass-energy
causes spacetime to curve---in way
that is **NOT** easy to perceive for relatively small mass objects like the
Earth---but that can be measured.

Features:

Image link: Wikipedia: File:Spacetime curvature.png.

Local file: local link: spacetime_curvature_earth.html.

File: Relativity file: spacetime_curvature_earth.html.