Document how Geo cursor works

What does this MR do?

Updates Geo documentation and adds additional explanation on our architecture.

Are there points in the code the reviewer needs to double check?

Please double check grammar.

Does this MR meet the acceptance criteria?

• Documentation created/updated

What are the relevant issue numbers?

Closes #3145 (closed)

cc @stanhu @dbalexandre @nick.thomas @jarv