Can someone please explain what the abbreviations mean.

I see a lot of people using abbreviations and i am relativey new and havn't worked them out yet.

IMO - i presume this is 'In my opinion'

LOL - what is this?

There are also some others that have gone from my mind. If someone would explain them and add extra ones I would be more than greatful.

"laugh out loud"

If you do a search you can find meanings for the abreviations
IMO- In my opinion

For more commonly used abbreviations, read this FAQ here.