> is the shell redirection operator. See What's is the difference between ">" and ">>" in shell command? and When should I use < or <() or << and > or >()? It is primarily used to redirect the output of a command to a file. If the file doesn't exist, the shell creates it. If it exists, the shell truncates it (empties it). With just
> file, there is no command, so the shell creates a file, but no output is sent to it, so the net effect is the creation of an empty file, or emptying an existing file.
touch is an external command that creates a file, or updates the timestamp, as you already know. With
touch, the file contents are not lost, if it exists, unlike with
The behaviour of
> depends on the shell. In bash, dash, and most shells,
> foo will work as you expect. In zsh, by default,
> foo works like
cat > foo - zsh waits for you type in input.
man bash. It's a long document and will take days or even weeks to understand well, but it's well worth going through if you want to learn Bash thoroughly.