What is Location?
Location is reference to location where the Activity happens.
Rules
If the location does not exist yet, you have to create it in first place. You can browse for existing locations here.
How this field works?
Enter part of the name and the field will display some suggestions. If necessary type more to narrow down options. Note that there must be [uid: xxx] displayed on the line where xxx stands for a number. Names are for humans, the systems cares only for the id number. So don't remove it.