How to lock a hand to an object in Blender like how locking works in SFM?

[Awaken]

I'm trying out Blender 2.8, in particular trying out animating.

I've used SFM a lot in the past, and it's super easy to animate a character holding a weapon since I can lock a weapon to the character's hand and zero out the playhead so the weapon follows the hand in whatever movement I give it.

I'm messing around with free models available from the internet, and using their rigs to animate hand movements and legs in Blender. I can't figure out how to attach something to the character's hands like how I can in SFM.

How can I achieve a similar result in Blender? Any guidance, tips, or videos that can help me is much appreciated. I'm willing to take the time to learn, just not sure what I'm looking for (terms, keywords).

[The Renderer]

You'll want to make the hand a "parent" of the weapon. First place the weapon relative to the hand the way you would like it to stay. Now select both the weapon and the hand but make sure the hand is the active object (e.g. by first selecting the weapon, then shift-selecting the hand).
Finally press Ctrl-P and select "Object" in the pop-up that comes up.

Now you can move and rotate the hand and the weapon will move with it as if they are one object.

https://www.youtube.com/watch?v=4tj7C3f2yQw

For more complex relationships between objects look up "constraints".

[Awaken]

That's awesome, thanks a bunch mate!

To further delve into this, one more question. Would I use parenting as well if I wanted a hand rig to follow another hand rig? So instead of objects, this time it's rigs. For example, handshaking. One hand leads the shake, the other kinda follows it. Is it even possible to have rigs parented like the above video?

Thank you for the "constraints" term, I didn't know about this. Watching videos on it now.

[The Renderer]

Not sure what your rig looks like but you can basically parent anything. Empties, bones, etc.

Whether you would actually do that for a handshake animation I am not sure. Maybe if you animate the first character and then use inverse kinematics with your parented hand to automatically get the second character's movements. But I'm not an animator, so that might be a really dumb idea from me. ;)

Edit: Little addendum: "Rigging" just means setting up a character/object with controls that you can then use to animate the character/object. So when you say "hand rig" it's not clear what that rig actually looks like, it could be a bone of an armature or some kind of empty that just controls the hand via constraints or something else entirely. Hence my first sentence above. If you don't know what I am talking about, don't worry. You probably have a bone setup and yes, you can parent and constrain any of the bones to anything else.