(are you sure it is < and not > ?. If it is really > then continue reading)
It's the line continuation prompt. Means the command you are typing in is expecting more input.
For example try this: grep then quote
$ grep '
telling you more input is expected. Just ^c and it will kill the command you are typing in and start again.
You could finish the line. Say in the example I posted if you added the closing quote then the command will run
If foo.txt looks like:
Pandora:~ frank$ cat foo.txt
Then grepping like this returns one thing:
Pandora:~ frank$ grep '
But grepping like this returns soemthing else:
Pandora:~ frank$ grep hello foo.txt