what are local folders?

I’m using the Wizard to set up my email.The last question is about Account Folders Location
Store Messages in Local Folders or
Create Separate Folder Tree
I don’t understand the difference between these 2 choices.I am using Outlook Express and would like to keep the same folders and format that I now use.

if you choose create separate folder tree eM Client will create new expandable account-named tree at your Mail tab. The other option will store messages at Local Folders plus-expandable tree (always existing at Mail tab).

All of previous apply to POP3 account creating (i.e.local). If you want to manage your account with folders stored at server create IMAP account.

I’m only using one POP3 account for now so I used the ‘Store in local folders’.
If I add my Gmail account at a later time,can I set it up as a POP3 account,also?

That shouldn’t be a problem.