What is the difference between a folder and an archive?

Question

I am learning about .tar.gz files while reading about the gzip utility. I read here that tar utility is used only to create an archive and not for compression.

So why do we even need archives when they are same as directories? (A collection of files and folders.)

Answer 1

So that you can put a directory structure into a single file, which makes it possible to send it to someone or to save it. Then they or you can reconstruct the directory structure from that file.