In geometry, we say that a line is DEFINED by two points:

 

But, a line isn't just made up of those two points.  It's made up of a TON of points -- an infinite number, in fact!

Check out these lines:

 

The equations of these line critters usually have
an
x guy and a y guy...

Here are some examples:

3x + 5y = 15

x - 6y = 6

y = 4x + 1

y = -2x - 3