Explains about what are the different Field Types/DataTypes in Salesforce..?

In the Field Types/DataTypes in Salesforce,nearly 21 datatypes are available.
They are shown below :

1.Auto Number :

            - A system generated sequence number.It uses display format whatever we define.

            - Automatically incremented for each new record.

2.Formula :
           - It is used to build formula(fields)datatype.
           - Formula fields are always defined based on another field value.
           - Formula datatypes contains different datatypes.
                1.number         2.date         3.date/time       4.person         5.currency           6.text
           - All formula fields are read-only fields,which can't be entered by user,which are calculated based on another fields.

3.Roll-up Summary :
           - It is used when there is relationship between Objects.
           - By using roll-up summary,following result can be achieved
                   - to count number of record objects
                   - to identify minimum value.
                   - to identify maximum value
                   - to identify average value
                   - to identify sum value.
Note :
       - Roll-up summary is enable,when there is always relationship with other objects.
       - Roll-up summary is created always for " Parent " object.

4.Look-up Relationship :
           - creates a relationship that links this object to another object.
           - The relationship field allows users to click on look-up icon to select a value from a pop-up list.The other object is the source of the values in the list.

5.Master-detail Relationship :
           - creates a special type of parent.child relationship between this objects(child/detail) & another  object( parent/master) where
                  - the relationship field is required on all detail records.
                  - once the value of the Relation field has been saved,it can't be changed.
                  - the ownership & sharing of a detail records are determined by master-record.
                  - when user deletes the master-record,all detail records are also deleted.
                  - we can create roll-up summary fields on master records to summarize the detail records.

6.Check box :
           - allow users to select a true(checked)/false(unchecked).

7.Currency :
           - It allows user to enter amount in different currency.

8.Date :
           - allows users to enter date values from calender.

9.Date/Time :
           - allows users to capture date/time value.

10.Email :
           - allows user to enter email address,which is validated to ensure proper format.

11.Number :
           - allows users to enter any number or it is used to stored numeric values.

12.Percentage :
           - allows users to enter data in percentage(%) format.

13.Phone :
           - It is used to enter phone number of different formats in different countries.

14.Picklist :
           - allows users to select a single value from a list you define.

15.Picklist(multi-select) :
           - allows users to select multiple values from a list you define.

16.Text :
           - it allows users to enter any combination of letters and numbers and any special characters.

17.Text Area :
           - allows users to enter upto 255 characters in multi-line.

18.Text Area(long) :
           - allows users to enter text upto maximum 32768 characters.

19.Text Area(Rich) :
           - allows users to enter text/image upto maximum 32768 characters.

20.Text (Encrypted) :
           - allows users to enter alphabets and numerics in encrypted format.(Ex. passwords)

21.URL :
           - allows users to enter valid website address.