Musical notes can be compared to letters of the alphabet. Random letters (or notes) do not make words, but when they do they mean something. So letters can make up words (or licks to make the comparison to music).
When different words are placed after each other in the right way they make up sentences. You can look at the term 'phrasing' as speaking sentences with your instrument. And when you are 'speaking' you make music.
Sorry if this is confusing, but I cannot fully remember the way it was explained to me. Hope this helps in some way.
Riffs usually are that short repeated parts of the song that make you recognize the song in an instant. You can look this video to get an idea.http://www.youtube.com/watch?v=xiC__IjCa2s
Hope this helps.
JJ