The phrase "free agent" refers to a person who is not tied to any specific organization or company. They have the freedom to choose where they work or who they work for, without any obligations or contracts. Full definition
The picks range between third - and seventh - round picks, and are awarded to teams that lost high - priced free agents in the year prior. (sbnation.com)
Per the collective bargaining agreement, international players can join the league as free agents if they wait until they're 25. (sbnation.com)
Two of the four players you listed are free agents after this season. (sbnation.com)