It is a term that applies to college athletes. A student-athlete by default gets to play at the college level for four years. There are only two exceptions to this rule. The first is for medical reasons. For example, a student who gets injured on the first play of the first game in football. It knocks him out for the year. The injured athlete can apply to the NCAA for an extension beyond his four years. This is usually for one year. This called medical red shirting.
The second exception is when, for whatever reason, a coach decides that he won't need you to play during your first year at college. The coach can red-shirt you and extend your eligibility for one year. You can practice but are not allowed to do anything but set the bench during games.
Sit out a year because of injury to preserve a year of eligibility
The home England football shirt is white and away is red.
He loses his redshirt status.
He has a football shaped head. He wears red overalls & a yellow shirt.
While both recipients of grey and red shirts attend classes at a school before participating in football games, the difference is in the player-to-be's time of enrollment:Via John Mackovic of The Desert Sun: "Grey shirt is a term used to designate an incoming freshman who waits until the second semester to enroll rather than the fall. Collegeathletes are allowed a five year calendar to play four seasons. The calendar begins once one is enrolled. By waiting until the spring to start college, a player will be playing his last season in the sixth year after high school rather than the fifth. "In contrast, infoplease.com explains that "When a player is given the "red-shirt" designation by his or her coach, that means he or she has participated in a college's academic year, but did not participate during that year's sports season. Most likely a "red-shirt freshman" in college football is a sophomore in college who practiced with the team his first year, but did not play in any games (at the coach's request), or was seriously injured during his first season." By redshirting, a player gains an opportunity to learn schemes and techniques, rehabilitate an injury, learn a new position and/or physically develop without losing a year of eligibility.
No...a high school football is smaller than a college football
Soccer itself has no "red shirt" rule. The term "red shirt" as applied to college athletics is about eligibility to, in general, play for "another year" because a player "sat out a season" due to injury, scholastic performance or the like. The particulars may require a good bit of interpretation, but they are set down in the case of college athletics by the NCAA. A link to their site is provided.
Boston College Eagles