How Brute-Force Matcher works?

edit

1 - Can someone explain to me with more details how the Brute-Force Matcher works?

The documentation explains very well how to use this method, but it is not too detailed on how the method works.

The documentation basically explains it:

Brute-Force matcher is simple. It takes the descriptor of one feature in first set and is matched with all other features in second set using some distance calculation. And the closest one is returned.

Just one more thing, about the distance measurement that is used, the documentation says:

By default, it is cv2.NORM_L2. It is good for SIFT, SURF etc (cv2.NORM_L1 is also there).

2 - What distance measurement is cv2.NORM_L2? Is it the euclidean distance?

Note: I am testing it with SIFT.

Thanks