When filtering activity cards two of the searchable attributes are Activity Title and Activity Type (among many other searchable attributes) Activity Title is the title that was given to an activity card, in this example the title would be "Quarterly Review". The Activity Type is the specific type of activity that the card is now associated with, "Internal Activity" would be the activity type in this example.
It is possible to add another user to an activity card or assign an activity card to someone. Create the activity card and click save. Open the activity card you just created and click the + on the top far right of the card. Begin typing the name of who you want to be added to the card and click save and then close.