My new .apk overwrites the old one on the same phone. why?

Hi,
I install the first .apk and test it successfully. I make another .apk (with the same keystore if it matters) and try to install it on the samme phone besides the first app. It promps "the file already exists. Do you want to overwrite it?
So when I press "ok" it overwrites the old app so I on ly have one app (the new one) instead of two?
Why it happens?
Ho do I fix it?

Another thing is that although it overwrites the old app it keeps it's name. So the new app shows by the old name (name of the 1st app).
Why? How do I fix it?

Thanks in advance

PS.: specs: I have Android 2.3, 3.0 and 4.0 (quadcore) - same result on all 3 devices.

It could be if you have given your app/game the same package name (it can be changed under the Android tab in the application properties)

Naturally, if you install a new version with the same package name, it will overwrite (update) it.
If you were wanting two separate apps, then you'd assign a different package name, usually as com.yourcompany.yourapplication .

Make sure your package has a unique name, so it doesn't overwrite/remove other apps with the same name!

As for the old name, changing it under the About tab in the application properties should change it to the new one when you re-built the APK... and has the same package name.

Thanks Again lh37! You also helped me with another topic just before :) !
Now I know what a "package name" actually Means. Because before I just thought that by Building an .apk under a new name should do it. Well, it doesn't, and now I know it :-) . Another problem solved I guess :-)

Thank you very much :)

You're welcome! :)