I guess a seed is someone downloading an item and a leech is someone uploading it!

Well these are a bunch of things I see heeps of and still dont 100% know what they are

So the more Seeds the faster the download speed?

So do I go for files with more Seeds or less Seeds or do i go for files with more Leeches or less

The more seeds a file has the faster it should go. Thats the idea behind seeders/leechers : you arent relying on just one person/place to dl from. the more leechers that are on a file , the more strain / bandwidth is being used from the seeders. Try to find an equally balanced file ; equal number of Seeders and leechers. Best situation is more seeds than leechs.