What does "refresh schema" do?

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I'm new to C5 and not a developer so I have some newbie questions:

What does "Refresh Schema" action do?
What does the "Refresh core database tables and blocks" option beneath it do?
When should I use these actions?
Are there any risks I should consider when using these two actions?

P.S. I am using a custom theme.

Thanks!

 
Mnkras replied on at Permalink Reply
Mnkras
you should not have to touch either of those, they are used to set the database schema if it becomes corrupted somehow, running them should not have adverse affects, but if you don't need to reset the db schema, then don't use em.
admin replied on at Permalink Reply
Thanks Mnkras!

I seem to be having trouble with permissions that I'm discussing on this thread:
http://www.concrete5.org/community/forums/customizing_c5/can-i-hide...

Basically, users in a group that has only "read" permissions for a page are seeing the top toolbar when they shouldn't.

Is it possible that refreshing the schema could fix that issue?
Mnkras replied on at Permalink Reply
Mnkras
I did not see that issue, and refreshing the schema will not fix it.