If we can hit it we can kill it
This is ways to check to physics system for information.
A raycast shoots a ray of a selected length from a position and return information about what object have been hit. Often used with a collision filter so one only hit the types of objects one care about. Another type is a linecast that work the same way but returns all the objects intersected by the line.
A sweep test is like a raycast that is using a shape instead of a line. So in a Spherecast one move a sphere between two points and see it hit's anything one the way.
A query takes a shape and return all the object that touch it. So a sphereQuery can be used to get all objects in range that will be damaged by a grenade.