sort reads lines, from files or from standard input, and writes them in order.

learner@tidepool:~$ sort names.txt
ana
ben
chen

Numbers: -n

Without a flag, sort compares characters from the left, the same as words in a dictionary. For numbers, that gives a wrong order:

-n compares the lines as numbers.

Reverse: -r

-r reverses the order. sort -nr puts the largest number first.

A column: -k

Lines often have columns, separated by spaces. -k2 sorts on the second column:

learner@tidepool:~$ cat sales.txt
tea 3
cake 12
coffee 9
learner@tidepool:~$ sort -k2 -nr sales.txt
cake 12
coffee 9
tea 3

In a pipeline

sort is often in the middle or at the end of a pipeline:

learner@tidepool:~$ grep cake sales.txt | sort -k2 -n