need help for understanding open cart concept

hello.
i am a regular forum poster. I don't know what is the use of Store name in system>settings. Can anyone tell me details?
What is the use of the section report>sales ?
Can i make users that can only do this sales>order>view>print invoice. and can change order status. But they can't delete any data.
what is the difference between access and modify permission?
please comment . thanks

There are tutorials and blog postings galore on these topics. Please use Google, it works great.