The AnalyticaVersion system variable encodes the current release number of Analytica. The actual value is an integer, encoded as:
major*10000 + minor*100 + patch
For example, for Analytica 3.1.2, AnalyticaVersion = 30102.
If you create functions whose implementation depends on the release of Analytica (for example, they may take advantage of functionality introduced in a more recent release), you can condition the functionality on this value. For example:
If AnalyticaVersion<40000 Then Old3_1Algorithm else New4_0Algorithm
Lumina has stopped using the term "Version" to indicate release number. We now use the terminology release, or release number for this. However, this function has existed for over 10 years, since way back in Analytica 2.0, and since its whole purpose is to distinguish release number so code can run across multiple releases, the old name shall remain.