It is a description, but to me, the 'at the end of the street' is the important qualification/limitation that makes using 'the' possible. It is what makes it 'the', rather than 'a'. What you are communicating by using 'the' and a qualification, is that there is (or at least should be) only one option you can be talking about. If I said "I'm going to the Freshchoice in town", and the person you were talking to knew there were in fact two Freshchoices in town, that person's reaction to that statement would be "Which Freshchoice?" - whether they say it or think it. * Sometimes part of the qualification is obviously implied, e.g. you are probably limiting it to something local. * Obviously this isn't the case when you have defined which 'the' you are talking about previously.

"- There is a supermarket at the end of my street. - I'm going to the supermarket at the end of my street" In the first sentence, "a" refers to any supermarket and not one in particular. For instance, it is possible there is more than one supermarket at the end of the street. You are not referring to any one special supermarket. You are simply saying there is at least one there, and you are not being specific. In the second sentence, "the" refers to one supermarket in particular. Not to any supermarket, but one in particular.

I’d say you’re definitely thinking in the right direction. “There is a supermarket at the end of my street” is the *first mention* — before you said that, your friend didn’t know there was a supermarket at the end of your street. In “I'm going to the supermarket at the end of my street”, it’s a given that there is one (and only one) supermarket at the end of your street. Yes, in the second example, “at the end of my street” defines / restricts the meaning of “supermarket”, so that we know which supermarket you’re referring to (making it definite). In the first example on the other hand, “at the end of my street” tells us for the first time of the location of a supermarket that you are mentioning for the first time (of which the listener was presumably unaware). Also, note that we usually use “the” to refer to places that we visit regularly: the supermarket, the bank, the office, etc.