ls

List directory contents. More information: https://www.gnu.org/software/coreutils/ls.

List files one per line:

ls -1
List all files, including hidden files:

ls -a
List all files, with trailing / added to directory names:

ls -F
Long format list (permissions, ownership, size, and modification date) of all files:

ls -la
Long format list with size displayed using human-readable units (KiB, MiB, GiB):

ls -lh
Long format list sorted by size (descending):

ls -lS
Long format list of all files, sorted by modification date (oldest first):

ls -ltr
Only list directories:

ls -d */