The y intercept is 3
You can also say that the y intercept is at (0,3) which is a more detailed answer. However saying "y intercept is 3" is sufficient enough because the x coordinate of the y intercept is always x = 0.
The y intercept is the location where the graph crosses or touches the y axis. This is at the halfway point between the 2 and 4, so (2+4)/2 = 6/2 = 3