When you have finished this page and think you are ready, go to the Lines, Rays, Angles Quiz.
A point is a location in space.
A line is a collection of points along a straight path that goes on and on in opposite directions. A line has no endpoints.
A line segment is a part of a line having two endpoints.
A ray is a part of a line with one endpoint and goes on and on in one direction...
Parallel lines are lines that never intersect or cross one another.
Perpendicular lines cross each other or intersect at right angles.
An angle is two lines that meet at an endpoint called a vertex. An angle can be named by the three letters that form it or by the letter that is at its vertex. An acute angle is one that measures less than 90 degrees with a protractor  that is how much the angle is open or the lines diverge from the vertex.
This would be A on the angle.  
Vertex or Point B of the angle  This would be C on this angle  
Acute Angle
ABC or Angle B

An obtuse angle has a measure of greater than 90 degrees at its opening as measured by a protractor.
Two angles whose measure in degrees adds up to 180 degrees are supplementary angles. An angle of 180 degrees is a straight angle and looks exactly like a line. In the above picture, A and B are supplementary to one another.