The idea here is that you put a consistent color in the background of your video and then replace it later with a still or moving image, thus creating more interest and eliminating the need for studio sets.
A "real" green screen is expensive, as is "real" greenscreen paint, but the good news is you can do it yourself more cheaply.
Simply obtain a hard, smooth surface and paint it a color which will never appear in the foreground. This is why hot blues and greens are favored -- they tend not to appear on the clothing or body.
Recommended board types would be hardboard, then MDF, then sheetrock or plywood. Simply prime them and paint on your hot, non-matching color.
Lighting of the screen needs to be very even and so you want the person/object as far away as possible from the screen. You will need lights for both the subject and the screen. 1000 watt lights with diffusion material such as "ToughSpun" are recommended.
Another tip: lighting the subject's head from above helps with the "dark halo" problem.