When you add a client, this opens up lots of different information you can store and things you can do. Information you can store for each client includes Contact Details and general information, detailed Comments, fully customisable Trackers and Image storage. With a client added you will be able to send them Invoices or Subscriptions, Book Appointments and create To-do's for each specific client. You won't be able to do these things without adding the individual as a client beforehand.
With the features available for you, you will be able to keep all the relevant information about each client and manage your day-to-day admin activities.
The other pages in the "Clients" category will go into more detail about storing information about your clients and how to set things up to fit your needs.