Short answers, pulled from the story.
"Maggie May" is a traditional Liverpool folk song about a sailor who returns home from Sierra Leone, is robbed of his wages and clothes by a prostitute named Maggie, and reports her to the police. She is found guilty of theft and sentenced to transportation to Botany Bay. The song names real streets in Liverpool, including Lime Street and old Canning Place.
The song dates back at least to 1830, when a reference to an early version appeared in the diary of Charles Picknell, a sailor on the female-convict ship Kains bound for Van Diemen's Land. That early version featured a protagonist called "charming Nellie Ray" rather than Maggie May. British sea music historian Stan Hugill describes it as a foc'sle song of Liverpool origin that became popular among seamen worldwide.
BBC Radio banned the Vipers Skiffle Group's 1957 recording of "Maggie May" because of the sexual content of its lyrics. The song's subject matter involving a prostitute who robs a sailor was considered unsuitable for broadcast at the time.
The Beatles recorded a 39-second version of "Maggie May" during their Get Back sessions in early 1969, playing it as a joking warm-up in heavy Scouse accents. It was included on their 1970 album Let It Be as the last track on the first side, spelled "Maggie Mae" on the track listing. It is the second-shortest song on any official Beatles album, after "Her Majesty" at 23 seconds.
Lionel Bart, the composer and lyricist, wrote the 1964 musical Maggie May, which used the traditional folk song and its backstory as the basis for a show set around the Liverpool Docks. The musical ran for two years in London. Bart kept the traditional tune but rewrote the lyrics, transforming Maggie from a convicted thief into a heroine whose departure from the streets is lamented.
Rod Stewart has said that the traditional Liverpool folk song "Maggie May" inspired his own 1971 hit single of the same name. Stewart's "Maggie May" reached number one in the United States, the United Kingdom, Australia, and Canada, though it is a distinct, original composition rather than an adaptation of the folk song.