This ADR defines a modification to the the governance module that would allow a staker to split their votes into several voting options. For example, it could use 70% of its voting power to vote Yes and 30% of its voting power to vote No.
However, often times the entity owning that address might not be a single individual. For example, a company might have different stakeholders who want to vote differently, and so it makes sense to allow them to split their voting power. Another example use case is exchanges. Many centralized exchanges often stake a portion of their users' tokens in their custody. Currently, it is not possible for them to do "passthrough voting" and giving their users voting rights over their tokens. However, with this system, exchanges can poll their users for voting preferences, and then vote on-chain proportionally to the results of the poll.
The governance tally function will iterate over all the options in a vote and add to the tally the result of the voter's voting power * the rate for that option.