A horse’s lead is which set of front legs advance first in a gait, such as trot or canter. The right lead is when the horse’s inside front leg reaches forward first, while the left lead is when the horse’s outside front leg stretches further forward than the inside leg with each stride. A horse’s sensitivity to the leader’s body language and cues is what determines the lead it takes in different situations. This link ravenox.com

For example, a barrel racer who knows that they will need to turn both the right and the left barrel in a cloverleaf pattern will try to start their horses on the correct lead before they enter the arena. This is because the horse is more likely to take a correct lead when they are already in an arena setting, and this can make them more confident and comfortable.

The Multi-Functional Lead: How to Use Different Styles for Various Activities

The most common way for a handler to lead a horse is with the leader standing in position two, or “herd of two.” In this position the leader walks alongside the horse nose to tail while the leader holds the lead rope over the shoulder and a few feet behind the horse. This allows the leader to control the horses’ movement while also having an opportunity to talk to the horse without putting pressure on the head. The advanced horse person can also use this position to invite faster motion or transitions from the horse, as well as teach herding exercises and other more complex maneuvers.