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whatever post you made using esteem app, They will be beneficiary of the full reward of that post with the percentage of 25, for example, if your post made 100 sbd, they will get 25 out of it :)
I hope you'll get it now :)

So if i make a post with esteem app, do i gain more or they gain more?

whatever will be the payout of your post, they will get 25 % of it.

That's terrific...... Does this apply to just them or every other people who upvotes my post?
And please..... Which app is most preferable?

no app is profitable, they are taking their percentages.
So try to you steemit.com only through google chrome.

it will be applicable to the net earnings of your post.

Oww dear, thanks so much