What is Default (50% / 50%) in Steemit post rewards?

In the rewards section when you are posting something you have three options.

1. Power Up 100%
2. Default (50% / 50%)
3. 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