A common question we have seen when filtering is "What is the difference between the filters "to Campaign" and "by Campaign"?".
In Kindful you can filter for Contacts and their association with giving to particular Campaigns. This article goes over the differences between the two filters used to find contacts and their associations with Campaigns: To Campaign and By Campaign.
The simplest answer to this is that one is for filtering directly for Contacts, and the other is for filtering directly for Activities.
When filtering contacts, you are looking for everyone who has given "to" a campaign.
When you want to filter the activities, you are wanting to keep them in order "by" which campaign they are attributed.
By Campaign is used on the Activities page. With this filter, you are looking for all activities that came By (way of this) Campaign.
To Campaign is used on the Contacts page. With this filter, you are looking for contacts who gave To (this) Campaign.
The reason you can filter for To Campaign on the Activities page is that the contacts are an attribute of the Activities (e.g. Sarah Smith made a $100 donation). But, you don't see By Campaign on the Contacts page because what you are searching for (Contacts) is different - you're looking for more broad elements of contacts (have they ever given, have they given to a particular campaign, are they in a particular region, are they in a group, etc.).