spectators at a golf or tennis match
"The gallery cheered loudly as the player hit an incredible ace down the line."
a room or series of rooms where works of art are exhibited
"After visiting the crowded gallery, I still couldn't decide which painting was my favorite."
a covered corridor (especially one extending along the wall of a building and supported with arches or columns)
"The tourists wandered through the stone gallery, admiring the ancient frescoes painted on the walls above their heads."
narrow recessed balcony area along an upper floor on the interior of a building; usually marked by a colonnade
"The rain forced us to retreat into the gallery where the stone columns kept the water from reaching our books."
An institution, building, or room for the exhibition and conservation of works of art.
"After weeks of searching online, we finally visited a local gallery to see their new collection of impressionist paintings in person."
In plain English: A gallery is a room or long hall where art, photos, or other items are displayed for people to look at.
"We spent the afternoon looking at paintings in the art gallery."
Usage: Use "gallery" to refer to a public room or building where paintings, sculptures, or other artworks are displayed for viewing. Do not confuse it with "galerie," which is simply the French spelling, or use it when you mean a long covered walkway unless specifically discussing an art exhibition space.
To show off
"He spent all afternoon posing by the window just to let everyone know he was rich."
In plain English: To gallery means to display something in an art gallery, but this word is almost never used as a verb in everyday conversation.
"She decided to gallery the new photos on her phone so everyone could see them."
Usage: As a verb, gallery means to display or exhibit something, often in an art context. It is not used to mean showing off; that usage is incorrect.
The word "gallery" entered English via Middle French and Old French to describe a long portico or covered walkway. Its ultimate origin is likely the name for the region of Galilee in Israel, which was originally used to refer to a church porch before shifting to its current architectural meaning.