Present progressive vs. present
I've been trying to teach myself spanish by using a wide variety of resources, one being this site.... I just watched the present progressive lesson and this tense is supposed to be like I am buying a dress (Estoy comprando una vestida) but in a textbook I read that the present tense (Estoy compro) could mean: "I buy", "I am buying" and "I do buy". Why would we learn the present progresive if the present tense could mean the same thing?
Thanks! 
6 Answers
Although they are often used interchangeably, the present progressive is used to emphasize that an action is in process and happening now.
In English, we have largely replaced the simple present with the present progressive. However, in Spanish, present progressive is used to emphasize you are right in the middle of some action.
By the by, the present progressive for comprar is "estoy comprando" (if the subject is yo), but the present is simply "compro" (no estoy).
The present progressive indicates that you are doing it right now. The present indicative, conditional, and future tenses can all be used to refer to the present, past, or future. The problem isn't with the Spanish tenses. it is with the English names for them.
alicia, I believe web and pescador have provided the correct answer, but I have noticed some liberties taken in the language. For example, a worker on break talking on the cell phone might say "estoy trabajando hoy" when he is really on break at the precise moment.
There are several other threads on the forum that address this question. You'll get read some interesting responses if you do a search on "present progressive".
Rosetta Stone starts off by teaching the simple present.
Yo bebo, yo compro, tú comes, etc. They teach the personal pronouns at first so you understand I, you, he/she/it, etc., but then start to remove them as the course goes on.
Later they will start introducing the present progressive... then the past and imperfect... then the future.
Like webdunce said, the pictures that go along with the present progressive show the person, or people, right in the middle of doing something.
Same thing with the online sessions with the tutors... in the earlier sessions, they'll show pictures and the tutor will ask what is going on. Everybody will say something like, "ella lleva una camisa", for example. Later, in the sessions that go along with the higher units, people will start to answer, "ella está llevando una camisa".
I know the textbooks teach that "Yo compro" means "I buy" or "I am buying", but I tend to think of "Compro" as "I buy", and "Estoy comprando" as "I am buying".
I'm not sure I understand your "Why" question.
Yes, it could mean the same thing and sometimes it does mean the same thing. You are learning a new language that is different from English in how the words are put together and what they mean--sometimes but not always.
