XF 1.4 Speed my forum up and questions?

[Dr.Who]

Hey guys, I wanted to ask some questions. What is the best way to speed up my forums performance? I have a VPS, utilize image optimization... but that's about it. I would do something related to "cache" but don't really know what it is and how it works.

Any ideas and some explanations for a noob like me would be fantastic.

Please be patient with me,
Clever Moniker