The less command can be used to display a file or the output of a command. It is sometimes referred to as a pager because it paginates text that won't fit onto a single screen.
$ls|less
This will list the files for the current directory with less.
By default it will even display a small amount of text output within the pager. If you want less to output text that fits onto a single screen directly to the terminal, you can pass the -F and -X flags.
$ls|less-FX
The -F flag tells less to exit if the output fits onto a single screen. The -X tells less to skip screen clearing.
This is handy if you want the output of a command to show up in your shell history.