Initial view
The initial view style. Visitors can change this, and the skin will remember this setting for awhile.
Initial zoom
Can be 0 to 20, where 0 is the globe, 20 is the most detailed available map. The index page map will try to match the map to contain all the placemarks.
API key
You will need to get an API key from Google as of 06/2016 Google has disabled the free access to Maps API. It's still free quite a large number of Map impressions per day, but be aware it's not free for massive Map usage anymore.
Click the "Create new/Manage" link on the UI to get to your Maps API console.
Read about their billing here: Understanding Billing for Maps