This is named the X Taping because you will form the letter X between your finger joints with the tape with this method. This is one of the most popular finger-taping methods and is extremely easy to learn.
You start off by placing the tape below the DIP (distal interphalangeal) joint, which is the closest joint to the tip of your finger. Wrap the tape over it twice and move down towards your next joint in a diagonal line.
When you’ve reached a point just below the lower joint, wrap the tape over it twice, as you’ve done the first time. Now move the tape back up until you form an X between the two joints. Repeat the process until the tape has enough thickness to it.
This method is popular because it offers great protection for your fingers while not restricting their movement.
BJJ Stripes explains the first method very well: