A transversal is a line in a plane that intersects two (or more) other lines, which are on the same plane, at distinct points.
Transversal Angles
In the figure, the line t is intersecting two coplanar lines $l_1$ and $l_2$. The line t is called the transversal of the lines $l_1$ and $l_2$. Here, the lines $l_1$ and $l_2$ may or may not be parallel.

Transversal angles are the angles formed by a transversal and the lines cut by the transversal. If a transversal intersects two coplanar lines, it forms four angles at the intersection of each line and the transversal, as shown in the figure. These eight angles are called the transversal angles.