The non-tender deadline marks the annual decision each MLB team faces on whether to offer or "tender" a contract to the arbitration-eligible players on their roster.
If they tender a contract, the team and player can continue to negotiate a salary figure for the upcoming season in an effort to avoid an arbitration hearing. If they do not tender a contract, the player is considered to be "non-tendered" and immediately becomes a free agent.
The biggest name cut loose at last year's non-tender deadline was Milwaukee Brewers right-hander Brandon Woodruff, though that ended up being more of a procedural move as he was re-signed to a new deal that better lined up with his Tommy John recovery timetable.