An activity is anything your organization "does." Typical activities include Meetings, Parties, Fund Raisers, Walks, Tournaments, etc. Activities can have specific Start and End Dates (including start and end times), or they can just "exist" without any associated date.
Using MemberTies Professional, you can also associate members with activities, and track associated postings. Each associated member can have a unique role (i.e., "Chairperson", "Speaker", etc.), and must have an attendance status (i.e., "Confirmed", "Declined", etc.). Any posting items will automatically be summed and displayed as an overall balance. You can add multiple members to an activity directly from the Membership List. See Adding Members to an Activity for details.
You work with activities via the Activity List. To get to the Activity List, choose File > Workspace > Activity List, or click the Activity List toolbar button.