Those are scan lines, an artifact from old CRT televisions. Lots of ways to make them, but the easiest is using the grid effect. Create a solid, add Effect > Generate > Grid. Change “Size From” to “Width & Height Sliders”. Change your width to a number larger than your comp and then move the Anchor Point. Then change the height to a really small number, like 4 and change the border to 2(adjust it to your taste. Then overlay using a blending mode and adjusting the opacity. You can make the grid move by animating the anchor point.
Johnny Cuevas, Editor
Thinkck.com
“I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”
—THOMAS EDISON on inventing the light bulb.