du is the usual command to show disk usage in a terminal, printing a list of all files and folders and subfolders the folder you ran it in contains. A barely readable list — to my noob’s eyes at least.
ncdu (NCurses Disk Usage) turns it into something much more useful, imo, putting forward the biggest folders first in a simplified way:
Use the arrow keys and Enter to navigate the folders.
To install ncdu on Manjaro/Arch:
sudo pacman -S ncdu