Pipes are very powerful. They can be chained to solve many problems. So, most of the commands are built in a way that they can be used with pipes as long as they read from standard input (keyboard or pipe) and write to standard output (screen or pipe )
Such programs that can be used with pipes are generally called filters. Command examples of filters are:
wc - for counting the letters, words, and lines in the input
grep - displays only the lines from the input in which keyword (which is passed as argument) is found.
sort - sorts/orders the input lines lexically (alphabetically) by default but can be changed
more - displays the input in a page-wise manner
cat - displays the content of the file passed as an argument
sed - substitute a word with another word: sed 's/word/another_word/'
tr - translate character ranges. For example to lowercase characters in input you can use:
tr 'A-Z' 'a-z'
uniq - Display the uniq input lines. The input lines need to be sorted. If you want to display frequency, use: