What does 925 AMM means that is ingraved inside my ring?

The engraving "925 AMM" on your ring indicates that it is made of sterling silver, which contains 92.5% pure silver and 7.5% other metals, typically copper. The "AMM" part could refer to the manufacturer or designer's initials or brand name. Sterling silver is known for its durability and lustrous appearance, making it a popular choice for jewelry.