What problem does this solve or what need does it fill?

Querying for specific components of entity is easy, but finding all of its components is necessarily hard, since it would require an exclusive system. This is particularly challenging for beginners who are attempting to understand the ECS or some specialized feature of it.

What solution would you like?

Add a Command that prints / provides information about the specified entity. Component names would be the MVP, but component contents may also be worth including if a suitable debug method exists for them.

What alternative(s) have you considered?

Implementing Debug for a World or a Query could also work well, and might be a nice complementary solution. See #1130 for this.

Serializing entities into a Scene could also work well, but still requires good introspection capabilities and is somewhat unnatural when you only want to quickly examine the results.

Additional context

This functionality would be very useful in the context of an editor: see bevy-inspector-egui for a wonderful prototype of this in a GUI context.