How do users get permissions in MySql when they log into my website?

I have a MySql database set up called users. The usually things compulsory to register to my website have been a username as well as password. When this is completed, a database populates with a users info as requested. How does MySql have this brand new users permissions to have it where they can right away download files from my website? As of right away any one can download as well as take my sites files but logging in. How do we stop which also?
Thanks in allege for any help.

How is OR done in where clause of mysql statement?

In an sql matter like:

select * from TableName where condition1 OR condition2 sequence by Timestamp

will a condition1 ALWAYS be searched for initial as well as afterwards condition 2 or does this matter demeanour during both during a same time as well as whatever comes loyal initial will be selected?

I wish to equivocate carrying 2 mysql statements to exam for condition1 initial as well as usually if which is false, exam for condition2 ?