These are alternatives to divorce litigation. Either option may cost substantially less than conventional divorce. That preserves your financial resources. If you want to accelerate resolution, one of them may be a better choice for you than going to court.
In mediation, you have an independent third party assisting you and your spouse in working out an agreement. You still have your lawyer advise you, and put the agreement into writing. Many people find mediation is far less emotionally draining that litigation. Another benefit is that mediated cases tend to be settled more quickly. Sometimes resolution can be accomplished in months, as opposed to the multi-year scenario for many litigated divorces.
Like mediation, arbitration is usually faster than full-fledged litigation. With arbitration, you agree to have your case decided by an arbitrator rather than a judge. The decision is binding, and can't be appealed. Even when arbitration is preferable to a lawsuit, it still leaves the final decision in the hands of a third person. This is another reason why it's advantageous to negotiate with your spouse if possible.
Because each divorce case has its own special circumstances, you'll need to consider these approaches carefully with your attorney to see if one of them is a better choice than a potential nasty, drawn out court battle.