They are what cheddar is before being formed into blocks and aged. Cheddar cheese is typically aged from 60 days to 4 years before being sold, whereas cheese curds are eaten straight away. While you can find mozzarella cheese curds, or other types of cheeses, it's almost always cheddar.
Players are signed and can be as young as 16. International players must be 16 to sign a contract. The universal age a player must be to play major league baseball is 16. The age limit is literally limitless. Once you get your high schooling it goes from there and you can be in the MLB which is usually around 18 for most people.
In short, if a player wants to be frugal and save what will eventually come to a lot of money, he can do it. And hereâs a little known fact about MLB pensions clipped from BusinessInsider.com : MLB players must play 43 days in the majors to earn a minimum $34,000 annual pension plan. Just one day in the majors gets them lifetime healthcare coverage. After 10 years in the big leagues, benefits grow to $100,000 annually.