It means that if there is no contract signed before the arbitration, both parties will give arguments to an arbiter of why the contract (one year only) should be a certain amount. The arbiter will then decide between the two amounts.

It's an option to avoid because the player will receive harsh criticism in the process that will make him want to leave once the contract is expired or before.

He is a special class of RFA (Restricted Free Agent) that either him or the club can elect to have a hearing with an impartial arbitrator to determine his next contract (with specific conditions) once the arbitrator has ruled the club has the option to sign that contract, or let the player go to free agency. That is a very high level view, I'm sure if ive misses any key points someone will be happy to jump in and correct me

One big factor around this is that the act of filing for arbitration also gives the Leafs a second buyout period regardless of if the arbitration even happens.

Because Sammy filed, now we can buyout Murray, AND they may agree on an extension before arbitration happens anyways.

Samsanov' Qualifying offer was 1 year 1.8mil. he elected not to sign that