"Al" is a contraction of "a el". For example: Yo voy al trabajo. This is correct. Yo voy a el trabajo. This is wrong. When you write "a el" , you must write "al" , But if it is an own name, like: cities, places, etc.; you must write " a El". Examples: Yo viajo a El Cairo. Is correct. Yo viajo al Cairo . Is wrong because El Cairo is an own name. The word "a" is only "a". Example: Yo voy a trabajar.

Edit: I see someone answered when I was typing.