Refers to the silver medal awarded in competitions, typically for second place.
彼はオリンピックで銀メダルを獲得した。
He won a silver medal at the Olympics.
金メダル is the first-place (gold) prize, while 銀メダル is the second-place (silver) prize in the same competition.
Compound of 銀 (gin, 'silver') and メダル (medaru, from English 'medal').