What are the Activities in Salesforce?

To create the Activities, while creating the object, we should check for 'Allow Activities' check box then user can add open Activities and Activity History related lists on the Object layout.
There are two types of activities -

1. Task: Task is nothing but work assigned to a particular person, it doesn't have certain time limit.
2. Event: It has certain time limit in that time only all persons should assemble after the time limit over, event will get complete.

- Once event or task status changed to 'Completed' then we can see those records under Activity History Related List.