What are humidity domes?

I've heard alot about humidity domes. Could someone please dumb down what they are for me?

Also are they vital for the growing process (i believe they are used with clones)? Do they hold any advantages etc?

Any help appreciated

Thanks guys

a clear dome that goes over your clones to keep humidity up.

i dont use one. i bubble clone.

Some growers use them for seedings. If you don't have enough humidity and can't get it higher domes can help the plant get a good start in life.

I use a clonning dome and have had great succsess when starting seeds. If u decide to go down the path, I have fond placeing a bacK heating pad under the dome while seeds are spouting very helpful also.
GL n Happy Growing