An actress - any actress, who happened to be there would have problems getting out of her car (a car) The actress - this particular actress couldn't get out of this particular car (the car)

Hi "Who am I", ILya has perfectly explained the difference between the two sentences. Now here is the difference between "a/an" and "the". A and AN are indefinite articles. "Indefinite" means "not specific". Use A(AN) when you are talking about a thing in general. "I have a phone." "Do you have a phone." "The" is a definite article. "Definite" means "specific". We use "the" when talking about something which is already known to the listener or which has been previously mentioned, introduced, or discussed. For example: "I have a phone. The phone is black." "Do you know where are the car keys?" NOTE: "The" is also used for singular and plural nouns. For example: "I saw the kangaroo at the zoo." "I saw the kangaroos at the zoo." Hope this helps. Alex