Show Flags

They are a means by which you can show or hide many of the items that are viewed within the viewport. For example, you can hide all particles, all landscape objects, or something a bit more advanced like turning off all the spotlights from a scene.

Example of Flags - Lighting Types:

More information about Show Flags:

https://docs.unrealengine.com/5.1/en-US/viewport-show-flags-in-unreal-engine/