Challenge Parkour are courses that are meant to 'Challenge' you. Alongside with completing the challenges, you get a prize for every challenge you do. A Challenge Parkour may have levels in it (as seen in Challenge 1). It uses carpet to demonstrate where to go if you get stuck and also uses green carpet as checkpoints or else it wouldn't be much fair.
To get to the Challenge Lobby, simply do /lobby challenge. You can also access it through the nether star > cake which brings you also the lobby.
(More coming soon)