Where in the documents system are applications mounted?

I have actually mounted a couple of Android applications both with the adb install MyApplication.apk command and also using a webserver (like a choice to Android Market).

Yet where in the Android documents system on my phone is the MyApplication.apk documents positioned? Are applications mounted with adb install not positioned in the very same directory site as applications downloaded and install from the marketplace?

I located some applications on /system/app yet I can not identify them as some downloaded and install from Android Market or the one I have actually mounted with adb install.

Where on the system is applications that I have mounted situated?

My phone is not rooted, and also I am running Nexus One with Android 2.2.1.