You might want to check out our step by step guide here (link :fishinglab.net/how-to-read-afishfinder) for more complete information.
Generally, here are the important things to consider:
The hard bottom in most models is displayed as a blue line with yellow above it, and the area above it to the surface level won’t display any color.
Any objects suspended from the bottom might or might not be a fish, pay attention for arches, a strong sign that it’s a fish.
A ball shape is usually a bait ball, so when there are larger objects around the ball, these are usually predatory fish.