The 30 Day Governance Staking Period is the time between when $HIVE is powered up and it can actually vote in governance issues. This is a security measure that was implemented as a result of Justin Sun's takeover of Steem.
Staking of the base layer coin provides a number of use cases on the Hive blockchain. The list includes:
- increased voting power which affects curation rewards
- increased resource credits allowing for engagement with the network
- voting on governance issues such as proposals and witnesses
- increased payout Hive Power due to the inflation adjustment
When one powers up, most of these go into effect immediately. The exception is the change in governance voting. Of course, one can always vote and any stake in the wallet outside of the recent power up will apply. The additional stake, however, will be withheld from the vote until the 30 day passes.
At that time, it will automatically be applied without any further action on behalf of the user.
The main idea is to give the witnesses time if an attack is underway. Any large moves in coins that are then powered up can be researched and questioned. Ultimately, if the action is viewed as a security threat to the blockchain, action could be taken to neutralize it.
This is only application to coins that are powered up. Hive Power that is distributed as part of the reward pool. The HP paid out to content creators and curators are immediately applicable to governance.