It allows groups of accounts to vote on and enact proposals without a full chain governance vote. Certain proposal types can then be decided on quickly in emergency situations, or low risk parameter updates can be delegated to a smaller group of individuals.
Committees work with "proposals", using the same type from the `gov` module so they are compatible with all existing proposal types such as param changes, or community pool spend, or text proposals.
A permission acts as a filter for incoming gov proposals, rejecting them if they do not pass. A permission can be any type with a method `Allows(p Proposal) bool`. They reject all proposals that they don't explicitly allow.
This allows permissions to be parameterized to allow fine grained control specified at runtime. For example a generic parameter permission type can allow a committee to only change a particular param, or only change params within a certain percentage.