In the rewards section when you are posting something you have three options.
- Power Up 100%
- Default (50% / 50%)
- Decline Payout
To understand what each of these does I am creating three posts each with one option. 
If you know what each of these options do and how to use them effectively let me know in the comments. If not I will share my learnings once I learn about them.
https://steemit.com/steemit/@gokulnk/what-is-power-up-100-in-rewards
https://steemit.com/steemit/@gokulnk/what-is-default-50-50-in-steemit-post-rewards
https://steemit.com/steemit/@gokulnk/what-is-decline-payout-in-steemit-post-rewards
Ohhh I just found the option. Finally! I was looking all over for it, lol. Thanks!
In my amateur understanding it means;
you can get your reward in either 100% steam power or split it 50 50 in steam power and steem itself or get nothing at all.
Yep well almost exactly. 50 50 split is sbd and steem power
Thank's for the post. I was looking for these answers. And finally found this.
I still don't understand how it works, who am I splitting the 50/50 with, and wouldn't I want 100% of the rewards?
All the rewards are yours. When you say 50/50 50% of the rewards comes as Steem Power which gives you influence in the community and better returns over the long term. The remaining 50% are awarded to you as Steem/SBD.
I found this link https://steemit.com/steem/@bacchist/psa-don-t-select-100-sp-rewards
However it is an old post, trying to understand it.
When SBD is greater than 1USD it makes sense to select 50% SBD and 50% SP. When SBD value is less than 1USD it makes more sense to go with PowerUp.
Good article, dont forget to VOTEUP ...
Essentially, I think for new users it would be better to go 100% to get more steem power, then later do the 50/50 split once you acquired more POWER.
When SBD = 1 USD it would make sense. Since SBD is higher than Steem, it might be better to go with 50%-50% for now and then convert your SBD to SteemPower.
I've had no idea you can do that. Guess for now then, just going everything with 50/50 is the way to go.
Thanks @gokulnk
100% power up means all of your shares of the earnings goes to powering up your account with Steem Power.
50/50 means you want some (half) to go to Steem Power and some (half) of your earnings from the post to go to your money account (either Steem or Steem Dollars) that are readily available for trade or to pay for stuff.