When to use a and when to use the?

Use 'a' the first time you mention a thing, then after that use 'the'. For example:

I noticed a restaurant so I went in and ordered a steak. When it came, the steak was tough and stringy. I spoke to the manager of therestaurant and told him I wouldn't be coming back.

A:The use of a, as in a general, unspecified thing: and use the when being specific.

In simple English, both Words mean " one ".

" a " means one of several or many possibilities.

" the " means " you know the one I mean " since I mentioned it earlier.

For example, a boy delivered a Pizza. The boy received a tip for bringing the pizza so quickly.