The shop is not only a shop, it has 4 sections:
You can buy stuff here. You can purchase emotes (250$) and sodas (5$) here.
You can buy gamepasses here. Use the package icon to gift a gamepass to someone.
Of course, with every game, comes merchandise. Buy clothing, worms, a pole, a door, and other things.
You can redeem codes here
Fun fact: You can squish the shop keeper by clicking on him, causing internal pain while exclaiming his pain via long exposition of text (dialogue).