Activity

Activity is the content that is received when a message is sent from WhatsApp and holds content of the message, type of message etc.

public class Activity
{
    public WhatsappMessage WpMessage { get; set; }

    public string Text { get; set; }

    public bool IsWelcome { get; set; }

    public string TimeStamp { get; set; }

    public string Value { get; set; }

    public double Latitude { get; set; }

    public double Longitude { get; set; }

    public Document Document { get; set; }

    public Image Image { get; set; }

    public Order Order { get; set; }

    public NfmReply Form { get; set; }
}

In the Activity object you can get above information about your users messages. Also, there are legacy function implementations of Activity to receive a lot more than you see above. Example:

Activity.GetProfileName(WhatsappMessage message);

WhatsappMessage object is the message you received from WhatsApp.