what kind of iphone do I have?

It is not the G3. I bought it from a friend (who bought from a friend)so there is no book. Says iPhone when it comes on, but the actual phone itself does not have an apple on it. Looks like the 4gb ( I think) but not entirely.Very bottom of touch screen has a house, an envelope, a book, a telephone and a music note symbols in white actually printed on the face of the screen. Below that, the round circle ( with small square in it) for navigating also has green phone reciever on L side and red on right to use to call or hang up as well as the red is to turn on and off. A dot is above each of these and are navigational tools. If I could figure out what this phone is I could order the manual and actually figure this phone out. Thanks.