It's a more informal way of saying "plus tard" (later) and is commonly used in everyday conversation.
Here's how it translates in different situations:
* "I'll call you later": "Je t'appellerai tout à l'heure."
* "See you soon": "À tout à l'heure."
* "We'll talk later": "On en parlera tout à l'heure."
There is no "tout a lour" phrase in French. It is likely a misspelling of "tout à l'heure".