In your party it doesn't do anything. Leading their own party it may effect slightly something they get regarding loot, they have some means that raises trade skill but I don't actually know how it works, it's something the player doesn't have as for the player only things you buy and sell for a profit gain trade, but AI parties do "something", probably just a cheat on their loot tbh.

Related: Mount And Blade II: Bannerlord - Best Infantry Units Leveling up your clan will allow you to have more troops in your party, recruit more companions, have other parties led by your

You are the level 1 hero. Alternatively, you can strip a companion of armor, shield, horse and give them a pitchfork from a looter. he wants a companion he can skill as he pleases from ground on, in stead of building up on a existing template. @ontrose afaik there are mods that allow you to alter characters.
In Mount & Blade 2: Bannerlord, these skills are essential to level up. Mount & Blade 2: Best Skills To Level Up. companions can take care of this skill for the player by being assigned as . 309 399 787 495 296 747 867 223

mount and blade 2 bannerlord how to level up companions