Titles are almost always important in poems and this one is no exception. First of all, the title functions as we described in the "Summary." It looks like, it sounds like, it is a description from a university course catalog. It sets us up for a scholastic setting and themes.
Oh, but we can't just stop there, now can we?
If we consider just the word "Introduction," we can see that the title works in some more under-the-radar ways too. First, we have "introduction" in the sense of being introduced to someone for the first time. What's so cool about viewing the word in this way is that it prepares us, ever so subtly, for the personification of the poem that takes place in the last two poems.
It's kind of like, "Poetry, I'd like you to meet our good friend Shmoop Reader. Shmoop Reader, this is Poetry." and then you're all, like, "Hi Poetry…cool sweater." And then Poetry is like, "Thanks, gift from my mom." And so on and so forth until the ice is broken and you and Poetry fall in love and live happily ever after.
Finally, there's "introduction" in the sense of getting the basics about something—the gist. Collins isn't trying to communicate every nuance of poetry appreciation. This is not "All You Need to Know About Poetry."
The word "introduction" in the title signals that Collins is giving us the survey course. And chances are, we readers are getting, in poetry form, the key elements Collins would probably include in one of his own introductory poetry courses. He is trying to give the reader a solid foundation to build on. Once you have the basics under your belt, then you're ready for the deeper, more advanced analysis.