The title of the song is very important; think of yourself as a salesperson who needs to pitch a product and the title as the name of that product. You would want your title to be memorable and fitting to the theme of the song. You should also highlight your title by placing it within the lyrics of the song.
In the AAA song form, titles are placed either at the beginning or end of each verse. In the AABA, the title usually appears at the beginning or end of the A section. In the verse/chorus and verse/chorus/bridge song, the title often begins or ends the chorus.
The verse is the part of the song that tells a story. Again think of yourself as a salesperson, you would need to use the proper words to convey information about your product in order to sell it. The verse functions the same way; it gives listeners more insight leading to the main message of the song and it moves the story forward. A song may have a number of verses, depending on the form, consisting of several lines each.
A refrain is a line (also can be the title) that is repeated at the end of every verse. Let's take our example for the AAA song form: at the end of each verse of "Bridge Over Troubled Water" the line (which also happens to be the title) "Like a bridge over troubled water" is repeated. The refrain is different from the chorus.
The chorus is the part of the song that often sticks to the mind of a listener because it contrasts with the verse and is repeated several times. The main theme is expressed in the chorus; the title of the song is usually included in the chorus too. Coming back to our salesperson analogy, think of the chorus as the slogan, the words that effectively summarizes why consumers should buy your product.
Differences Between Refrain and Chorus:
There is some confusion as to the function of the refrain and chorus. Although both have lines that are repeated and may contain the title, the refrain and chorus vary in length. The refrain is shorter than the chorus; often the refrain is composed of 2 lines while the chorus can be made up of several lines. The chorus is also melodically, rhythmically and lyrically different from the verse and expresses the main message of the song.
Also known as the "climb," this part of the song differs melodically and lyrically from the verse and comes before the chorus. The reason why it's called a climb is because it heightens the anticipation of the listeners for the coming climax which is the chorus. An example of a song with a climb is "If Ever You're In My Arms Again" by Peabo Bryson
We had a once in a lifetime
But I just couldn't see
Until it was gone
A second once in a lifetime
May be too much to ask
But I swear from now on
In the AABA song form, the bridge (B) is musically and lyrically different than the A sections. In this form, the bridge gives the song contrast before transitioning to the final A section, therefore it is a necessary part of the song.
In the verse/chorus/bridge song form however, the bridge functions differently. It is shorter than the verse and should offer a reason why the final chorus needs to be repeated. It also differs melodically, lyrically and rhythmically from the verse and chorus. In the song "Just Once" recorded by James Ingram, the bridge part begins with the line "Just once I want to understand..."
Coda is an Italian word for "tail," it is the additional lines of a song which brings it to a close. The coda is an optional addition to a song.