When using it presents you with a list of the 18 types + Stellar.
Choose a type from the list and you'll be shown the Type Chart for that Tera Typing - What hits it super effective, what its it not very effective, what deals neautral damage
Hover over the icons to see the type if your not able to identify them by looking as hovering over them will reveal :Electric: :Dark: etc -
This is visible only to the user who called the command
/typematchup command:
Permission Level: All Users
Works in all Pokemon Channels -
Command Syntax: Slash Command : /typematchup
Will return a table of single type matchups that will self delete in 60seconds - This is the full table for all 18 types - Visible to everyone for the 60s duration