Can I install a WP7 app directly to a phone?

I am wondering if it is possible to install an app directly onto a WP7 device. I don't know much about WP and don't have any devices. Do we need to submit the app to Microsoft or can we just download and install an app?

One of the nice things about Android is that we can get an apk and install it on a device. But for iPhone I don't think you can do this unless you jailbreak it or go through the developer tools.