An abbreviation version of a diagram doesn't include all the details. It's more like a rough diagram that shows only the essentials.

While 略図 can be used for any simplified diagram, it most commonly refers to a rough map that gives a basic overview of an area.

This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.