Depending on how the character looks, either capsule or sphere. Sometimes box.
You should consider collision carefully. What does it need to get blocked by, what does it need to overlap. What’s also important is what they detected as, this lets you create your own collision types which can be extremely useful.
These nodes are exactly what you want, maybe substitute “On even hit” is necessary sometimes, but you’ll figure that out. I’ll give you two examples. The one on the left is for checking whether a chest has contents and then spawning an emitter once my character gets within a certain range of it, the second one is for doing damage with a weapon capsule (sometimes you may want a DoOnce node here). Notice how I always check if it is overlapping the player character, not something else.