Calculated Created Date, Created Time, Modified Date and Modified Time fields are automatically created from the Time Stamps.
Timestamps are stored in UTC and returned/displayed in Local Time.
The Created and Modified fields are automatically populated when a record is inserted.
The Modified fields are updated automatically when user initiated changes are made to to records, note that this is not for all changes.
The Created and Modified status bar is displayed at the bottom of forms. It can be turned of for a User if desired in User Preferences.
Further tracking can be enabled using Change Tracking if desired.