Activities include tasks, events, calendars, phone calls, and emails. With Elements, you can track tasks and meetings together in lists and reports to easily prioritize your time and keep up with your Relationships, Portfolios, Contacts and Prospects.
Tasks, different than Requests, generally are internal actions that need to be taken by users at your firm, and don't necessarily need to be initiated by a client (Requests). Tasks include things like a Business Development call, an Internal call (maybe about a client or event) or an Administrative task that should be associated with a Relationship or Contact that the client isn't directly involved in.
Best Practice: Use Tasks to track information and notes about clients, rather than Client Notes. It seems counterintuitive, but Tasks and Activities allow reporting, exporting and auditing, where Client notes have none of these features.
Events and subsequent calendars can help you track meetings and upcoming happenings as they relate to your Contacts or Relationships. Events help you to track and record event details, and they can be a single event, or a recurring event.
The Events that you create and display on your Calendar. Calendars can be shared to help create efficiencies across your business.