100% Power up
100% power up means all of your shares of the earnings goes to powering up your account with Steem Power. This is what gives you a more powerful status and the more steem power you have the more influence you have on steemit.
50/50
50/50 means you want half to go to Steem Power and half of your earnings from the post to go to your money account (either Steem or Steem Dollars) that are available for you to trade or to pay for stuff.