To understand music and songwriting, you need to listen to it and understand the parts. Different people have different ways to name, handle and structure the different parts - I will present you with a way that has worked for me over 25 years now. Other people on the forums will surely disagree to some of my conventions (especially my view on "the bridge") - and you will need to figure out a way that works for you.
Most modern popular music is built up around verse and refrain, often dubbed as part A and part B. Part B often repeats in lyric while part A often are carriers of the story. The element sometimes (and mistakenly, in my belief) called "bridge" which is often put up to build between verse and refrain usually doesn't get it's own letter - most often it is too short for this. The bridge - which isn't in all songs - gets the letter C. It is usually different in melody, chords and lyrics and usually only happens once a bit out into the song.
That being the basics, let's try and apply this logic to well known songs:
First out, the Beatles of course. She Loves You:
Now this song is a great example of BABABAB structure. Starting out with the refrain part: "She loves you, yeah, yeah, yeah" which is repeating, and therefore the refrain - I dub "B". The first verse - starting with "You think you lost your love, Well I saw her yesterday (iay)" and ending with "Yes she loves you, and you know you should be glad" - is different each time and get's the letter "A".
There are of course different aspects to every song, and with this it is the ending. It repeats a couple of lines from A, then ends with the last part of B - with a twist. Try to see the structure behind the details before you analyze everything.
Ok simple song - but see how it already turned difficult, well - you will find Beatles often do that when you look closer.
Over to a truly simple one: Janis Joplin - Mercedes Benz
Now - according to me, those are all A - this song is all verses - three of them, making it AAA. Listen and see if I'm right ...
Another great example is Jimi Hendrix - Little Wing (with some excellent solos in-between).
Now we need an example of the C part - agree? Ok - over to:
Ozzy Osbourne - Dreamer:
Not with the bite he once had (pun intended), this song is an excellent example of what I mean with bridge - but first, let's establish part A and B - I'm sure you can do that by now. Part A beginning with the lyrics "Gazing through the window ..." and part B is of course "I'm just a Dreamer ...." ok?
Well - then it's AABAB .. hey! ... "Your higher power may be God or jesus christ" ... that's completely different. That's the bridge. Stamp it C and listen as it leads into a guitar solo on the A part (some people include that in their notes, some don't - I do).
So ... that's then AABABCAABB ... then - if you play this out a late night and people are dancing closely - you can repeat part B for as long as you like.
Now one of my favorite bands: Genesis and Land of Confusion.
This is another great example of the bridge part. First establish part A which is the "I must've dreamed a thousand dreams" and repeated in "Now did you read the news today" making out the AA.
What comes next is where there are a lot of different practices - the part that starts with "Too many men" and the part starting with "This is the world we live in" - are both just as long, and very different. Should they be two parts?
I tend to not do this and make this whole repeating section part B - the whole part is used over again like it is later and if you start using too much letters for describing the different parts of the song you soon end up a too complex system - imagine trying to detail Bohemian Rhapsody for example.
Anyway - so we have AABAB - and here comes the part with something completely different again, even with halving the beat: "I remember long ago ...". This is the bridge, or part C - making the whole song structure like this: AABABCAB
End notes
Remember that this is a system for understanding song structure and also describing and explaining to band members or others what you want to change with a song or what to play (it's a priceless tool with drummers, for instance - who often don't pay too much attention ... at all, really ...). Do not make this system an iron jacket you can't escape from - as important as analyzing the songs to find the structure is to find the parts of it which is out of structure. More often than not, that is what makes a song special.
Now - your home lesson: I want 4 analyzed songs by Friday!