caching question
 

I can write plugins easily enough, but I don't understand caching - at all.

I'm thinking of writing a very, very basic awards system (4 or 5 awards at most). I would create a custom user field and put individual awards in format "pic.gif", "alt text", separated by semi-colons. I would parse the text in the the plugin and create a variable (ie $awards="<img src=". imagename ." alt=". alt-text .">") which would go in the postbit template.

All of that I can handle, but I don't know what the impact would be on performance. Any help would be appreciated, on this and general caching.