A straight line doesn't have a beginning or an ending, and is formed by an infinite number of points all lined up. If we draw two lines (or representations of these lines), we have three possibilities: either never touch, or intersect once, or coincide at all points. Below you can learn what is the relation between two lines, so you can study maths more easily,
Two parallel lines are two straight lines that never intersect.
Two lines are said to be competing when they intersect at a point. That way we can have oblique or perpendicular lines, depending on the width degrees formed. If the angle is 90º, then these lines are said to be perpendicular. If the angle isn't 90º, then these lines are said to be oblique.
Two lines are said to be coincident if they coincide at all points.