My idea of an enterprise app store is that there is a page on the company's website where all the apps that that company developed for its employees are listed so they can use them. And access to this apps is restriceted to the employees of the company.
As far as I know you can download an Android App from any website and install it on an Andoid phone, you don't have to use Android Market. However installing an App that does not come from the Android Market is not that straightforward.
For Apple, you can only install an app from the Appstore, so how can you have an enterprise app store?
Please tell me what exactly is an enterprise app store. I think I got it wrong, also I read a lot on the internet for this keywords.