What are these unexpected databases no my MySQL AWS RDS instance?

On my AWS RDS MySQL instance I have some databases I didn't explicitly create there (and have never seen on my local MySQL databases, or on other hosted databases I've worked with) and wonder what they are (and what I can do about them):

information_schema
mysql
performance_schema    
innodb

The first three are filled with data that I don't understand (and are listed separately in my MySQL tools; e.g. I have no ability to control privileges for them separately), while the last is empty. Can I delete the innodb? What are the others (I assume I should leave them alone)?

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Forgive what may turn out to be a naive MySQL or AWS question; I'm fairly new to both.