One could say that a frame is the skeleton of the bicycle. All the components that make up the bicycle are mounted on it. And ourselves, of course.
At Santafixie we have frames from many brands (including our own), materials, geometries, sizes and configurations.
They can be made of steel, aluminum or carbon. For city use the most recommended are steel or aluminum frames. They are more resistant to possible knocks than carbon, and the difference in weight is not so important for reaching the next traffic light faster. If, on the other hand, you are going to train or compete on the track and the only thing that matters is cutting times,it would be worthwhile to opt for a carbon frame and lose the extra weight.
In terms of geometry, there are frames that encourage a more aggressive position, with the upper body very horizontal, usually for competing on track or simply to utilize the bike to the maximum. There are also geometries suitable for a more recreational purpose, like touring or city rides, for keeping the back in an almost vertical position. The commuter bicycles also use a type of frame for riding with an upright position, perfect for riding in the city because through having a higher position our field of vision is greater, thus improving the ability to react to any unforeseen events.
When choosing the frame for your future bicycle, you must also take into account the use you are going to give it and the components and accessories you are going to need or not. If you are going to need a bottle holder, saddlebags, if the brakes are going to be disc, v-brake or even without brakes, if you prefer internal or external wiring, the width of the wheel you are going to mount, etc ... The frame you choose must be able to mount each of these components the way you want or need.
If everything is clear, and you already know what you need, go ahead, now you only have to choose the colour you want.