If you are viewing Analytics within a segment, the Activity types considered when calculating Activities change depending on the specific view you are in.
View 1
You have selected Predictive Analytics, Behavioral Analytics, or Profile Analytics:
Visitors – the number of unique visitors to your website over the past 30 days
Keywords – the number of unique keywords researched by this account over the past 30 days. This includes both Generic and Branded Keywords. Keyword data is now limited to the previous 6 months.
Activities – the number of total activities over the past 30 days, on your website, as detected by 6sense. This includes pageviews, form submits, and video plays. Activities data is available for the previous 27 months.
View 2
You have selected the Total Accounts tab:
Visitors – the number of unique visitors to your website over the past 30 days
Keywords – the number of unique keywords researched by this account over the past 30 days. This includes both Generic and Branded Keywords.
Activities – the number of total activities over the past 30 days, across the following types: Website Activities (pageviews, form submits, video plays), B2B Network Research Activities, 6sense Media Matched Impressions, and External Media Matched Impressions.