A compound grind uses more than one grind geometry on the same blade, most often a flat or hollow grind high up with a different angle near the edge. It lets a maker tune thickness and strength independently at each part of the blade.
The commonest version is a high flat grind that thins the blade generally, with a convex or steeper flat section right at the apex for durability. Some Japanese kitchen knives use a hollow relief above a flat edge section for the same reason.
Look for two distinct grind lines rather than one. Where the angle changes, the reflection along the blade changes with it.
A compound grind can genuinely give slicing performance and edge durability at once, which single geometries have to trade against each other. It costs more to manufacture, so it usually appears on higher-end knives.
The same principle at a smaller scale is a micro-bevel, which is a compound geometry applied only to the last fraction of a millimeter.