Short answers, pulled from the story.
Preposition stranding is the syntactic construction in which a preposition appears somewhere other than immediately before its object, often at the end of a sentence. English examples include "Which town did you come from?" and "This is the book that I told you about." The construction contrasts with pied piping, which keeps the preposition with its object as in "From which town did you come?"
The earliest recorded disparagement is attributed to the 17th-century grammarian Joshua Poole. The controversy became widely known after 1672, when the poet John Dryden objected to Ben Jonson's 1611 phrase "the bodies that those souls were frighted from," though Dryden never explained his reasoning.
The phrase "stranded preposition" appeared in 1949. The term "preposition stranding" was coined in 1964. Before these terms existed, linguists described the same construction as a sentence-terminal preposition.
In his Dictionary of Modern English Usage published in 1926, H. W. Fowler called the ban on terminal prepositions a "cherished superstition" and devoted four columns to rebutting the prescription. He argued that the rule, when applied too strictly, produced sentences far more awkward than the stranded prepositions it was trying to prevent.
Preposition stranding is permitted in English, other Germanic languages including Dutch and Danish, and in the Niger-Congo languages Vata and Gbadi. It also appears in certain North American dialects of French. Spanish, Greek, standard French, and most dialects of Arabic require pied piping instead and do not allow stranding.
The preposition stranding generalization proposes that if a language allows preposition stranding under wh-movement, it will also allow preposition stranding under sluicing. The PSG does not hold universally; some languages ban stranding under sluicing even when they permit it in other contexts.