Can anybody please explain something to me,it may sound stupid but ive used chat on here loads of times but what exactly are all the options at the top for,what do they really do,thanks in advance

You mean the 'private chat' option?
If you hover your mouse over the icons it should show an explanation.
For example, if you click the 'clock' it will show the time the last message was sent.
'Smilies' give you an option of faces you can use...

The chat function is not very useable on some phones, so best to use a computer/laptop/tablet...