While most international free agents from Latin America sign as amateurs during their teenage years, Cuba has its own top professional league: the Cuban National Series (Serie Nacional). Players with enough experience as a professional in Cuba are exempt from MLB's international bonus pools.
Any player 25 years of age or older with at least six seasons in Serie Nacional is considered a professional rather than an amateur. These players may sign a Major League or Minor League contract with any team for any amount, just as a domestic free agent would, without penalty for the signing team.
Cuban-born first baseman Jose Abreu signed a Major League contract with the White Sox in October 2013. Major League Baseball had different international free-agency specifications at that point, offering unrestricted free agency to players aged 23 and older who had at least five years of professional experience. Given he was 26 years old at the time of the signing and had already played parts of 10 professional seasons in Cuba, Abreu would have qualified for unrestricted free agency under the current rules as well.
Note: The information contained in this glossary entry is subject to change as details emerge.