Voice policies in Lync Server 2013 define what features users might leverage with their Enterprise Voice service. This includes options such as simultaneous ringing, team call, or call forwarding. The other main component of voice policies is that PSTN usages are associated with a policy.
From a planning perspective, examine the various options of a voice policy and make a decision about how many policies are required. Policies can be global, assigned to a site, or directly assigned to user accounts.