Definition:Lines which don't meet each other or intersect each other, irrespective how much they are extended, are known as "Parallel Line"
Parallel Lines are also known as Nonintersecting lines.
In the above figure, you can see that Line A and B, even after being extended, don't meet each other at any point. Hence Line A and B are parallel to each other.
When two lines are parallel to each other, its denoted by sign ""
So, we write, Line A  Line B
Below are some more figures of parallel lines.
Figure 1
Figure 2
Figure 3

