I have 2 apple id for some reason & would like to delete one as it is very confusing how do I do this

Only iTunes Support can potentially delete an account, which will also delete any content that you purchased with the account (so you would lose the ability to authorise the content on a new computer or redownload it) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page

Or you could remove any personal info it (e.g. payment details if you have them on it) and not use the account anymore.