I am new to software development and I have a question about mobile development. I am creating an app that relies heavily on a users location, like Uber, and was wondering if you needed an API key for Google Maps in order to launch the device map application and present data on top of it?
To obtain the user's location you don't need Google at all, the Android SDK contains appropiate methods.
If you want to open the Google Map application from your app (leaving your app, opening Google Maps), you don't need an API key.
To display Google Maps in your app, you will need an API key.
It's easily obtainable though, have a look at the docs.