FORM: A poem may or may not have a specific number of lines, rhyme scheme and/or metrical pattern,
STANZAS: Stanzas are a series of lines grouped together and separated by an empty line from other stanzas. 
RHYME: Rhyme is the repetition of similar sounds. In poetry, the most common kind of rhyme is the end rhyme, which occurs at the end of two or more lines. It is usually identified with lower case letters, and a new letter is used to identify each new end sound.