Erecto is a spell used to set up a stucture of sorts. Hermione Granger, Ron Weasley and Harry Potter used this spell to set up a tent for themselves while hunting Horcruxes in 1997 and 1998.
Behind the scenes
- Erecting a tent is the only known use in the series, but it could presumably be used to erect any structure given that the required materials were present.
Erectum is past participle of erigere, a Latin verb meaning "to erect".