To have an idea about what geometry means, you'll have to cover the following curriculum:
First you need to know what are the tools of geometry.
Then you'll have to deal with the relative position of the lines (parallel or perpendicular)
Then you'll have to be aware what an area of a geometric shape means and what a perimeter means.
The next step would be the acquaintance with the most common geometric shape: triangle. Then you'll have to find out the relations between the elements of the triangle (angles and sides), relations that lead to similarity or congruence of the triangles. You'll have to discover what does it mean a right angle triangles, an isosceles or equilateral triangle.
You'll learn about the other geometric shapes: quadrilaterals and circles.
You also have to learn about the coordinate plane.
Once you're becoming aquinted with the plane geometry, you can move to another level, namely three dimensional shapes and their extensions.
A special chapter in geometry is the one concerning vectors. This chapter is very useful in other fields of science you' studying, such as physics.
The topics described above would be enough, for the moment, to give a very good idea about this field called geometry.