RE: Altered my steemvoter (curation=mining) account in preparation for HF 19
You can think of it as how much weight your vote carries. A vote at 100% will give twice as much to an author as a vote at 50%. It will also use up twice as much of your overall voting power. Quoting from the official blog post about HF 19:
As it stands now a single 100% vote uses only 0.5% of your remaining voting power (voting power regenerates fully over a 5 day period). That means real users would need to vote 40 times a day at full power to use all of their voting power.
The post goes on to explain what will happen after the hard fork takes effect:
After this change, a single 100% vote will use 2% of your remaining voting power, meaning that 10 full-power votes a day will now exhaust the majority of your voting power. Of course, if one does not wish to use this much voting power in a single vote, anyone is still free to lower the power-percentage of their votes accordingly.
I think an optimal strategy is to tweak your voting rules so that your overall voting power hovers around 80%. That means you are fully using up your 40 votes per day, but keeping your voting power high enough to provide good benefit to the people you vote on + good curation rewards for yourself.
You can see how much overall voting power you have by clicking on the "Get VP" button on the main Steemvoter accounts page.