Riff vs Lick

A riff and a lick are both short guitar phrases, but they don't play the same role. A riff is a phrase repeated on a loop: it forms the rhythmic and melodic foundation of a song, usually played by the rhythm guitar. A lick is a short, non-repeated phrase: it belongs to the vocabulary of soloing and improvisation, used to punctuate or close a musical phrase rather than structure it.

A distinction Guitarshelf's catalogue makes concrete

Rather than leaving this difference abstract, Guitarshelf turns it into two clearly separate sheet types:

• Riff sheets offer a 4-to-8-bar phrase, built to be looped — exactly the role a real song riff plays.
• Ending lick sheets offer a single-bar phrase, deliberately conclusive: it isn't meant to loop, but to close a riff or an improvisation, just like a real lick would in an actual song.

The best way to feel the difference: practice a riff sheet until you can loop it without hesitation, then follow it with an ending lick sheet in the same key to hear how it closes the phrase.