Here is how it applies to me and my musical experience.
Hook - this is the main part of the song and the most significant part that you recognize. This doesn't need to be guitar exclusively, but here are some examples of guitar "hooks."
Intro to "Sweet Home Alabama"
Main guitar part of "Smoke on the Water"
Verse guitar part in "Message in a Bottle"
Main guitar part in "Enter Sandman:The list is endless. Again, the "hook" is the most defining part of the song that people can hear just a snippet of and can recognize that it's a certain song.
Lick - to me this applies to soloing and is a lead guitar part that is characteristic to a certain player. A lick doesn't have to be the defining part of a song, but can be defining to a certain player and/or style. You will often hear, "play some blues licks" or "play a lick in the style of Jeff Beck." Again, to me this applies to lead guitar playing. Some may disagree.
Riff - a riff is a rhythm guitar part that has a vocal like quality and is not part of a solo per say. Here are some examples of some riffs. The riff can serve as the "hook" of a song, but a song can consist of many, many riffs.
Intro to "Mississippi Queen"
Main guitar part in "Noone Knows" (Queens of the Stone Age)
Nearly everything heard in "Black Dog"Hopefully you get the point. A riff is part of a rhythm guitar part, played on lower strings and can be used as the "hook" of the song just as easily.
Chop - Not sure about this. I have never heard of a chop within a song or in relation to this idea. You will often hear sayings like "that player has great chops", referring to someone's high level of playing ability. I would say this phrase doesn't play into this context at all. "Guitar Chops" are often referred to someone's level of playing.
Hopefully this makes sense. Feel free to post more questions and good luck!
Douglas Showalter