The salary arbitration process is pretty archaic. When players and teams exchange salary figures in mid-January, they are given the option to negotiate a contract. In most cases, the negotiations are fairly simple, and contracts are finalized by the mid-February deadline. In situations where both parties can not come to an agreement by the deadline, they're required to appear before an arbitration panel and plead their cases. These situations are often ugly, partisan, and uncomfortable.
The way the system is set up, nearly every player that files for arbitration ends up receiving a substantial raise. About half of the players are expected to agree to terms with their teams within the next week. Only a handful of the cases will actually get heard by the arbitration panel.