Lines farther apart would indicate a gentler gradient. Lines that jog in sharply would indicate a cut or draw. Lines that jut out indicate a point. Topographic maps contain both index lines and intermediate lines. Index lines are darker and are periodically labeled with numbers showing the elevation at that line.
Intermediate lines are lighter and often unlabeled.
You can tell the elevation by counting the number of increments between index lines. It takes a little practice to learn to use a topo map. You can simply study it over and over until you can visualize what every mark means, but the quickest way to become sharp with a topo map is to obtain one for an area familiar to you. Compare a topo map that includes the family farm or your traditional hunting area to what you know about the area and what you can see. Look for ridges, brushy draws and steep rock walls.