Task and Event

As per salesforce definition:

An event is a calendar event scheduled for a specific day and time.

Examples of events are:

1)      Meetings
2)      Scheduled Conference Calls

A task is an activity not scheduled for an exact day and time. You can specify a due date for a task or there may not be a particular time or date that the tasks or activities need to be completed by.

Examples of tasks are:

- A list of phone calls you need to make.
-  An email that needs to be sent.