There are many different songs, but modern popular songwriting, including folk, blues, pop and rock songs, build upon basic types of songs or "songs form." Understanding the basic song forms and their traditions helps the songwriter decide upon the appropriate structure for the type of songs she wants to write. Song forms can be broadly divided into the stanzaic and non-stanzaic, or elaborate forms that use the assigned letters "A", "B" and "C" and the "AAA" form. Commonly, the assigned letters are "A" for verses, "B" for choruses and "C" for the bridge.

Stanzaic Songs
Strophic, or stanzaic, songs have a single unit, called a strophe or stanza, that is repeated an indefinite number of times. Stanzaic songs are strongly associated with the folk music tradition. The ballad stanza consists of four lines in which the first and third beats are four beats long and the second and fourth lines three beats long. The first line can also be shortened to three beats. The second and fourth lines rhyme, and sometimes the first and third lines rhyme as well. The classic 12-bar blues song uses rhymed stanzas of three lines in which the second line repeats the first. The third line of the 12-bar blues song is the answer phrase, which musically and lyrically answers the statement of the first two lines.
  Verse-and-Chorus Songs
Stanzaic songs may include a refrain at the end of the stanza. Long and complex refrains are found in songs with a verse-and-chorus structure. When the words and music of the chorus are the same each time, but the verses have the same music with different words each time, the song has an extended refrain, according to Hartman. According to Money Chords, most popular songs from the classic rock period are written in the verse-and-chorus form, which has been around since the mid-19th century. A common type of verse-and-chorus song uses eight-bar verses and choruses.

Elaborate Non-Stanzaic Forms
Songs with verses and choruses strain the definition of a stanzaic song, because they alternate between the different units of verse and chorus. Elaborate versions of non-strophic songs are associated with Tin Pan Alley and show-tune songwriting, and the structures of these types of songs are assigned a letter. The most common non-stanzaic song structure is AABA. From the perspective of this type of songwriting structure, the stanzaic song form is "AAA," which is the oldest song form and is associated with folk music.

Regardless of what forms you are comfortable with, always ask yourself, why are you writing and who are you trying to reach? The idea is to connect emotionally with the listener. There are songwriting fundamentals and tools to do this that can make you stand out as a songwriter. They take practice but you can learn them. This may sound strange now but with time you’ll see it’s true.