Sorry to ask such a question, but can anyone tell me the difference between a Samsung Acc and Samsung Kies?

I have a S4 and have also just bought a Tab3 8inch. On both I have a Samsung Acc with the same log in details. I think both are now linked to this account. I have also been backing up my S4 to Samsung Kies. When I set up my tab, it automatically brought all my pictures that I had backed up from my S4 to my Samsung account onto my tablet - this was great.

What is the purpose of a Samsung Acc?

Does all my data from my S4 and Tab now automatically back up to my Samsung Acc?

Can I automatically set a back up option from my phone and tab to Samsung Acc?

If not, should I do this?

What does Kies do differently to Samsung Acc?

Any other tips?

Many thanks