You can choose whether or not your posts appear on your Fanpage when you create your posts:
It is worth noting the difference between a Promoted Post Ad Type, Published Post and an Unpublished Post.
A Promoted Post is simply an Ad Type which advertises a particular Post; this can be either an Unpublished Post and Published Post. The only difference is that Ads Promoting Published Posts show posts which exist on your fanpage and you are using your advertising to promote them; Ads Promoting Unpublished Posts how posts that you cannot find on the fanpage.
Using Unpublished Posts can be advantageous in that you can test out many variations of your creatives (so this is where you mix and match your different messages, calls to actions, images etc) but you choose to only display the most relevant version to your target audience, without having to clog up your Facebook Page with lots of posts!