The capos

Definition

The capo is a device that will block all the strings simultaneously on the same fret.
Its main use is to increase the basic tone of the open strings without touching the tuning: the length of the strings becomes shorter, and this gives higher sounds.

The use of the capo at different heights changes the perception of the neck of the guitar for the musician, offering new opportunities for composers, who very often use it.
 

The main types of capos

The strip capos

These are the oldest, hence the most commonly used, but not necessarily the best.
They can be good to start because they are cheaper.

The spring capos

These are the most recent, they have the advantage of being moved faster, being stronger but also better reflecting the tuning (but not necessarily true for all models).
Of course they are more expensive. Get it only if you are to use it regularly.

Other types of capos

As you can imagine there are many other types of capos, but they are all more or less variants of those mentioned above so we will not detail them here.

How to place it

Two techniques are possible: either place in the middle of a fret, or at the limit of the upper fret.

I prefer the second method which ensures less "frisage" of the strings, here's what it looks like visually: