Google Earth software is available in 5 types:
For each desktop platform Google Earth has Windows, Mac, Linux versions
For mobile platform there are Android, and iOS (iPhone) versions.
There is also a new automotive version as well.
You can still download older versions of Google Earth namely 6.2 through 5.1 from Google's direct download links. Best to uninstall Google Earth 7.0 (if unable to use that version) then install a clean version of 6.2 or 5.1 downloaded directly from google.com.Note, however, that street view is only supported in GE versions 6 and higher.Since Google has removed such versions of Google Earth then it isn't advisable to use those -- use the versions of that Google makes available. If you really want 4.3 or earlier versions then non-google web sites such as filehippo.com have those versions but you have to download at your own risksince Google doesn't authorize those web sites.See related link below.
The current version and several previous versions (including v6.2) of both Google Earth and Google Earth Pro for Windows and Mac can be downloaded from Google Earth's direct download site.https://support.google.com/earth/answer/168344?hl=en
In order to use Google Earth you need to download the application. There are versions of Google earth for all sorts of mobile devices available for download.
Yes, they are two different products of Google Inc.
The Google Earth Free and Pro versions have the same numbering scheme so the version itself doesn't tell you if what you have is Pro version or not. When you start Google Earth Pro it will have "Google Earth Pro" in the title of the window. You can also go to Help menu and select "About Google Earth".
I guess it is free to use however, you cannot distribute it on your own. In free version you cannot integrate your GIS data but there are another versions like Google Earth pro and Google Earth enterprise.
There is only one free version of Google Earth, so that'd be the best one out there. In total are only two versions of Google Earth: the free version, and the professional (paid) version.
As of the 6.0 release in March 2011 the 5.0 and 4.3 versions are no longer available from google's official web site. You can still use the direct installer links to download the previous versions (5.2, 5.1) for Windows and Mac. This web page also has links to download GE Pro versions as well.However, you can still download old versions of Google Earth (including 5.0 and beta versions) from the filehippo website. (This website is not affiliated with Google so use at your own risk.)
Here is one of Google's announcements of ending Street View support for Google Earth versions 5.x and older. "With the most recent update to Google Earth (6.2), we are also finalizing our transition to a new method of delivering Street View imagery in Google Earth. This means, that the older versions of Google Earth (anything before 6.0) will no longer be able to access Street View. We held off making this change until now, when the vast majority of Google Earth users are on 6.0 (or later)." -- Google Jan 2012. Basically, Google decided to improve the Street View interfaces which would be implemented in the current versions of Google Earth for desktop and mobile platforms rather than keep supporting the older (less efficient) method of accessing Street View.
As it did for earlier versions of Google Earth, Google offers a free version for normal usage and a high-performance Pro version for business users with an annual subscription.
Google Maps and Google Earth are two completely different technologies. Google Earth can be downloaded and placed on your computer and is more powerful and interactive.
One can get information on Google Earth at the official Google's website for Google Earth. Other resources are Wikipedia, different Google Earth related Blogs like Gearthblog, forums or the program's Help section.