MLB The Show 20 equipment lets you change and customize the appearance of individual players on your team. Equipment even gives buffs and bonuses to players with them.
You get equipment when you open packs or as rewards for Diamond Dynasty. Equipment give some modifiers to the player's stats. You can choose which equipment your players don, and even customize how it looks.
MLB The Show 20 Equipment: How to Customize Equipment
In Road to the Show, you can adjust all the appearances in one menu when you go to the Appearance in the Customize tab. The same is true for Diamond Dynasty, but for some reason you have to use a different menu to customize.
To customize equipment in Diamond Dynasty, you need to create a custom character first. Go to Created Player in your squad menu, and after creating a character you can select the Equipment tab. You can't actually change your equipment's appearance without going to Equipment.
Pressing Triangle over most equipment lets you edit and change the appearance of them. You can change the individual cosmetic appearances, down to having a finger out of a glove.
MLB The Show 20 is out now exclusively for PS4.