If you have stumbled upon this map directly from the Internet, there is an in-depth article that I recommend you read first which gives it greater context located here -
Regarding the map itself, you will find controls to show/hide markers relating to baptisms and probable travel routes for the various years, located on the right hand side of the map. Clicking individual markers will display information relating to that baptism.
The baptisms and travel route for 1836 are loaded for you by default as an example ...