Other forms: ex-votos
When religious offerings are left because of a vow that somebody made in prayer, those offerings are called ex-voto. Usually, ex-voto offerings are left on display.
An offering that is left on display is called a votive offering. An ex-voto is a specific kind of votive offering, and is common in the Catholic faith. Essentially, an ex-voto offering is made because you vowed to a saint or divinity that you would make it, but they can also be made just out of gratitude to that saint or divinity.