Blocks
Blocks are items which may be added to the left or right column of any page in Moodle. The Blocks link will take you to information about all blocks in Moodle. Blocks can be placed in a tab on the left side of the screen via the Dock icon – 
Navigation
The Navigation block appears on every page of the site. It contains an expanding tree menu which includes My Home, Site Pages, My Profile, and Courses.
Settings
The Settings block provides context-sensitive links to settings pages. What appears in the settings block depends upon the Page being shown. This block also appears on every page of the site.
Activities
The Activities block links to the different types of activities available in your course (Forums, Quizzes, Assignments, and so forth). The activities list will grow as you add activities to your course.
Messages
The Messages block displays a list of new messages you have received, with a link to your Messages window.
HTML
The HTML block is a standard block used to add text or images to a site or course page.
Calendar
The Calendar block displays events; for example, if due dates are set for assignments, these will be displayed on the calendar.
Upcoming Events
The Upcoming Events block displays future events in a summarized list. Events are generated directly from the calendar and/or activity deadlines, providing a link to full details or directly to the activity. There is no need to use the Upcoming Events block AND the Calendar block since they include similar information.
People
The People block contains a link to the list of the course Participants.