In many cases, you would like to have a quick overview of all activity over a certain period of time (i.e. today or this week). You can use several views which will help you get a quick understanding of the current status of projects and any open items.
1. To View Tickets that were opened today - From the Tickets window, click the filter check box and then the Filter... button. In the Field Name to filter by, select Open Date, and in the date value enter today's date (you can easily set the date for today by double-clicking the arrow which opens the small calendar window).
This will list all the Tickets that were opened today.
2. To View all the activity for today (or any other date range) - You can view all the activity from the History window. To open the history window, click the History icon 
in the left pane.
Here you can view a journal of all the activity in the system. You can filter it by date in the From filter on the top tool bar. You can also filter the activity for a certain employee, or create more complicated filters.
History Window
You can also view the activity history per Account or Ticket (see below).