I've been searching everywhere and can't find an answer to three questions:
1) What are MySQL and PostgreSQL for?
2) What's the difference between MySQL and PostgreSQL?
3) What is PHP for?
All help is highly appreciated. I've been looking into more advanced website design, and a lot of sites i've been to say i should also read up on MySQL/PostgreSQL and some even say PHP, but i have no idea what any of it does or is.