Hello Mayowa
I understand your confusion. When you implement the neighbor command, it is used to create the neighbor relationship. It is also used to configure parameters that pertain to the relationship. But it is never used to configure anything on the neighboring router. Whenever a route map is used in a network command, it always filters the advertisements on that relationship. The in or out keywords indicate which direction is filtered.
Now if you were to implement the command you state above, it would enable filtering for the advertisement of routes from R2 to R1. It does not affect the local BGP table, but it affects what information is sent to R1.
Now one option would be to use the same command but use the in keyword instead. This would work, but is not best practice, because it requires that the advertisement be sent, (which uses both CPU and bandwidth) and that it be filtered locally, (which uses CPU). It’s always better to filter closer to the source.
I hope this has been helpful!
Laz