A bicycle frame is made up of several parts: round, elliptic or hydroformed tubes, they carry the same names regardless of the bicycle type. The image below presents the name for each segment of the frame.
Headtube: the frame’s “neck”
Top Tube: the upper tube of the frame
Down Tube: the bottom tube of the frame
Seat Tube: the saddle tube
Chainstay: the inferior segment of the frame’s posterior triangle
Seatstays: the superior segment of the frame’s posterior triangle
Dropouts: mounting place of the rear wheel or front wheel (on the fork)
And now, a few details about the angles formed by the headtube and seat tube:
The headtube’s angle influences the bike’s steering. A steeper angle (70 – 71 degrees) is responsible for a more agile steering, while a shallow angle (67-69 degrees) will make steering slower yet more stable.
The seat tube angle is connected to the bike’s climbing abilities. The steepest this angle is (73 degrees or even more), the better your position on the bicycle will be on tough climbs.
The top tube length will decide your position on the bike, whether you’ll ride lying on it, or in a more compact position. So a long tope tube means a sporty position, but if it is too long, this can be corrected by installing a shorter stem.
The chain stay length also influences the handling of the bike. A shorter chainstay means that you will ride an agile bike, and also that you will be able to lift easier the front wheel, when pulling the handlebar. A longer chainstay will make your bike more stable, yet stealing from its agile character.