What does the Webmail icon do?

I set setting email parameters and was trying to test , but hitting "Webmail" icon the Setting-Advaced window showed up? Ho to use e-mail feature?

Set the URL you would like in the setting and it will be assigned to the icon.
A quick link to your communications.

Oh, I get it, but I thought that Lite Cart has it's own... Email configuration is for what?

No, I wish. But an email client is an entire app project of it's own.
The email configuration is for enabling the store to send emails using SMTP.