Blog Pages

Hi everyone,
So, I am setting up a blog page, and I went to “Pages” I saw 3 sample blog pages” as I also saw 3 blogs on create Menu. So I thought one is enough, I deleted the rest of 2 sample blog pages, but when I visit and viewed my site ( blog), it showed “error 404…”. Then I restored the 2 sample blogs pages again, the page appeared work just fine… anyway, my questions:

1. What is the purpose of having 3 blogs sample on “Pages” (not “Post”)? has this to do with some kind of links pages and I should not delete them?
For ref: On sample pages also has 3 sample My Account page, 3 sample Members, 3 Contact, and 3 callback. that made me hesitant to do anything with them.

That’s all for now. Thanks for your help 🙂