Geometry is the branch of math dealing specifically with points, lines, curves, surfaces including their sizes, areas, and volumes. From the Greek word "geo" (earth) and "metro" (measure), geometry allows us to determine sizes of various shapes, discover the volume of a shape (think of "volume" as how much water would fit inside of a soda can - the amount of water can be measured as volume.)
There are only a few important pieces of geometry that you need to know to be able to determine many types of problems; these, listed in no particular order are:
1. Finding the Area of a 2D shape.
2. Finding the Surface Area of a 3D shape.
3. Finding the volume of a 3D shape.
4. The Pythagorean Theorem
5. Miscellaneous smaller topics, such as line pairs, classifying lines and angles, etc.
We cover each of these topics and more in our Lesson and Tutorial Center: Math.