Two lines which meet are called intersecting lines.
Here, line l 1 & l 2 meet at point O.
So, they are intersecting lines.
Angles made by the transversal - Theory
Angles made by the transversal
Alternate Interior Angles
Exterior angles (when transversal intersects two parallel lines)
Alternate exterior angles
Proof of Alternate Exterior Angle Equal
Interior angles on same side of transversal
Ex 5.2, 2 Important