OK. A quick down and dirty lesson in song construction as requested by Dawn.
Parts of a song. Not all sections are used all the time. There are common forms for different styles ie rock or folk etc. Some use more some use less and the rules are broken all the time.
Intro. Usually instrumental. Meant to capture your attention and give you an idea of generally where the tune is going. It can be the chorus or verse used.
Verse This is where the story lives and builds. It tells what's happening and how you feel about it.
Pre chorus. This is used to build up to the chorus if needed using different lyrics or chords before you get to the bridge. It is often left out. Use as needed. Think of it as the setup for the chorus. You can also think of it as a mini bridge
Chorus. This is the part that makes or breaks a song. This is the part that you should be humming or singing as your walking down the street. This is where the hook lives, The title of the song first line or last. It is also where the phrase or riff that repeats through out the song lives. More than one chorus in a tune are usually identical with minor variations. Your audience needs to hear it enough to be able to remember it. Think of the chorus as the part that says this is what I learned from what happened in the verses and this is what i am going to do about it. So you can think of this as the pay off.
Bridge. The bridge sometimes called middle eight ie. usually 8 bars is considered a release. Common in rock after the second chorus but not needed in a lot of other tunes. Can have words or just notes. Think of the bridge as an interlude or a break between the other sections. The bridge is also not used all the time for all songs.
Outro or Coda. Think of it as the ta da at the end of a magic act. The grand finale that tells you the show is over and went out with a bang.
Now to put the pieces together keeping in mind that these rules can be easily broken if what your doing sounds good to the ear. Frustrating isn't it.
A= verse first section
B= chorus second section
C= third section Can be bridge or chorus
D= Bridge 4th section.
B and D are interchangeable. The letters refer to different sections of a song more than function.
Intros and coda or outros are in the first section and last section.
These are the basic forms
AAA. A straight verse form Church hymns and folk songs.
AA. Two verse Broadway and show tunes from the 40s to 60s.
AABA Verse and bridge. (This is most likely where your song falls Dawn so think folk or show tune type stuff unless you choose to add more sections) Another popular form of pre pop songs.
AABABA This extended version of the above is where pop comes in. It just adds another bridge and a final verse.
ABAB Most used today for rock, pop and Gospel R&B and country. Verse chorus.
Think Alice Keys Fallin. A really clear example . ABABC. C being the outro or coda. I love that tune BTW
Now it gets complicated so you might want to put the rest of this on a shelf for a while.
ABC Verse pre chorus and chorus. Think of the pre chorus as a mini bridge.
ABABC Verse chorus using a bridge
ABCABCD. Yikes! Verse chorus using both pre chorus and bridge
ie. A- verse1, B pre chorus,C chorus, A verse2, B pre chorus, C chorus, D bridge and then final Chorus or C.
At this point you can pretty much do what you want and skip sections since the listener has had so much time to get a feel for the tune.
You could just as easily do it this way.
A-B-A-B-C-D-B-A-C-B . Confused yet. This will help same thing defined
verse, pre chorus1,verse2, pre chorus2,chorus,bridge, pre chorus3, verse3,chorus, pre chorus4.
Ouch. That gave me a headache We are definitely in the deep end of the pool. There are tons of books on this subject, as I have said before this is a very deep topic. Probably more than you needed to know Dawn.

I gotta take a rest. I am sure ICjones can explain it better than I. Listen to songs and try to figure out what the sections of the songs are to get a feel for it.