Hey there!
There are various concepts that are used in the world of Geometry, however there are some simple concepts that may be easier to work with.
Simple Concepts in Geometry
- Points - In geometry, a point is a location represented often by a dot on a x-y graph. The point does not have any length, width, shape or size, it only has a position.
- Lines - In geometry, a line is a straight one-dimensional figure having no thickness and extending infinitely in both directions.
- Segments - In geometry, a line segment is a piece or part of a line having two endpoints. The length of a line segment can be measured either in metric units such as millimeters, centimeters, or customary units such as feet or inches.
- Rays - In geometry, a ray is usually taken as a half-infinite line (also referred to as a 'half line') with one or the two points and taken to be at infinity.
_____________________________________________________
So, in summary to all of this, it really depends on what concepts in geometry you are currently learning and which concept(s) you personally find the most useful and helpful.