Question 198657
It's a line.
This is a great tool for plotting things
http://www36.wolframalpha.com/input/?i=+x-2y%3D4

If you wanted to plot the line yourself, pick an 'easy' value for x and then find the y that makes the equation true. I like to pick x=0. 
{{{0 - 2y = 4}}}
{{{y = -2}}}
So one point is (0, -2)

Now pick a second value. I like to pick y=0.
{{{x -2*0 = 4}}}
{{{x=4}}}
So another point is (4,0).
Plot those two points and draw the line that connects them.

Anytime the equation you are given has a single power of x added/subtracted to a single power of y being set to some number, you have a line.