Theory:

Let us recall what a line, a line segment, a ray and an angle is.
Line:
If two points are extended endlessly in both directions in a straight path, a line is drawn.
Line.png
 
In the figure, the two points \(P\) and \(Q\) are extended endlessly in both directions to get a line \(PQ\).
 
The line \(PQ\) is denoted as \(\overleftrightarrow{PQ}\).
Line Segment:
The line connecting of two end points is a line segment.
line seg.png
 
In the figure, the line connects the two points end \(P\) and \(Q\) to form a line segment.
 
The line segment \(PQ\) is denoted as \(\overline{PQ}\).
Ray:
A line consisting of one end point or a starting point is a ray.
ray.png
 
In the figure, the line \(PQ\) extends endlessly from a starting point \(P\) to form a ray.
 
The ray \(PQ\) is denoted as \(\overrightarrow{PQ}\).
Angle:
When two line segments or lines intersect with each other, they form an angle.
angles.png
 
In the figure, the lines \(\overleftrightarrow{OA}\) and \(\overleftrightarrow{OB}\) intersect at \(O\) to form an angle \(AOB\).
 
The angle \(AOB\) is represented as \(\angle AOB\).
 
Important!
Click here! To recall the types of angles.