How to view a block in Minecraft by targetting on them? Like TDM does in mod review?

I see a lot of minecraft mod review and some of them have a block viewer or something. Whenever they hover over a block, it states the name at the top of the screen. Like in the picture. Is it a mod? Please help!
How to view a block in Minecraft by targetting on them Like TDM does in mod review - 1

Guest

Yes it is a Mod, the mod is called WAILA (What Am I Looking At)

It currently only goes up to 1.7.5

Ducky

That's WAILA (aka What Am I Looking At) it is a mod growing in popularity in many modpacks.

Thomas S