what is the difference between Campaign Member Status and Campaign Member Activity fields? They seem quite the same and i cannot understand their difference. Campaign Member status indicates the status of the Campaign Member in Salesforce. For Campaign Member Activity, it is said that it can be updated by Journey builder. But, why to have 2 fields since they seem to do exactly the same ? Can't Journey Builder update the Campaign Member status? Am i missing something here?
"Activity" comes through the Marketing Cloud Connect Package to avoid conflicts.
"Status" is a "normal" standard field that exists by default. It is targeted by the Marketing Cloud Connector for Campaign Member Tracking. However, since it IS a default field, it's not unlikely that it has already been used for something else.
In order to not create conflicts by wanting to use the capabilities of the Marketing Cloud Connect Managed Package, the Package comes with a second, dedicated field for the same purpose like "status" that is also supported by Campaign Member Tracking. So "Activity" and "Status" both are compatible with this feature, and you can assess the situation in your Sales Cloud Org to decide which one you want to use. Avoiding such conflicts is generally a good thing, so I would probably go for Activity, as it is reserved for this purpose only, and you can never really control against future plans involving standard fields.