A Prime lens is one that a fixed focal length. An example would be a 35mm lens. Prime lenses tend to have higher aperture capabilities at a lower cost. They also tend to focus faster because the focal length never changes.

Instead of stating whether to purchase it or not, I will list the pros and cons of buying a prime lens. The main difference between a prime lens and a zoom lens is that a prime lens can not zoom. However, without the capability to zoom, this encourages the photographer to move around and find alternative shooting points. Another positive aspect of using a prime lens is that it has a lot better image quality, with less fringing.

Information about choosing a Canon Prime lens can be found from sources such as The Wirecutter and PhotoNotes. These sources are particularly aimed at beginning photographers.

Yes! Manual focussing is easy and that is a great lens.

The f on a camera lens is the maximum aperture of the lens. It is sometimes listed as 1:X with X being the maximum aperture. For example:
- Canon EF 50mm f1.4 is a 50mm prime lens with a maximum aperture of 1.4
- Tamron 90mm f2.8 is a 90mm prime lens with a maximum aperture of 2.8
- Canon 70-200mm f/4 is a lens with a focal length of 70-200mm and a maximum aperture of 4.