How to create custom fields in salesforce

Field:
Fields is nothing but columns in table. It is used to store the data depending up on the field data type. Fields stores the data depending on the data type of the field. Now we will see the how to create different type of field.
1. Log in your Salesforce account using the user name and password.
2. Last post we seen how to create object. select Setup-->app setup-->Create-->Object. Here you can find all custom objects.Then Select an object to create a field.

3. Then look on Custom fields and relationships section. Then click on New button.

4. Then you can find the all the data type, Select the data type based on the type of information do you want to store.

Data Type	Description
Auto Number	A system-generated sequence number that uses a display format you define. The number is automatically incremented for each new record.
Formula	A read-only field that derives its value from a formula expression you define. The formula field is updated when any of the source fields change.
Roll-Up Summary	A read-only field that displays the sum, minimum, or maximum value of a field in a related list or the record count of all records listed in a related list.
Lookup Relationship	Creates a relationship that links this object to another object. The relationship field allows users to click on a lookup icon to select a value from a popup list. The other object is the source of the values in the list.
Master-Detail Relationship	Creates a special type of parent-child relationship between this object (the child, or "detail") and another object (the parent, or "master") where: The relationship field is required on all detail records. The ownership and sharing of a detail record are determined by the master record. When a user deletes the master record, all detail records are deleted. You can create rollup summary fields on the master record to summarize the detail records. The relationship field allows users to click on a lookup icon to select a value from a popup list. The master object is the source of the values in the list.
Checkbox	Allows users to select a True (checked) or False (unchecked) value.
Currency	Allows users to enter a dollar or other currency amount and automatically formats the field as a currency amount. This can be useful if you export data to Excel or another spreadsheet.
Date	Allows users to enter a date or pick a date from a popup calendar.
Date/Time	Allows users to enter a date and time, or pick a date from a popup calendar. When users click a date in the popup, that date and the current time are entered into the Date/Time field.
Email	Allows users to enter an email address, which is validated to ensure proper format. If this field is specified for a contact or lead, users can choose the address when clicking Send an Email. Note that custom email addresses cannot be used for mass emails.
Geolocation	(Beta) Allows users to define locations.
Number	Allows users to enter any number. Leading zeros are removed.
Percent	Allows users to enter a percentage number, for example, '10' and automatically adds the percent sign to the number.
Phone	Allows users to enter any phone number. Automatically formats it as a phone number.
Picklist	Allows users to select a value from a list you define.
Picklist (Multi-Select)	Allows users to select multiple values from a list you define.
Text	Allows users to enter any combination of letters and numbers.
Text Area	Allows users to enter up to 255 characters on separate lines.
Text Area (Long)	Allows users to enter up to 32,768 characters on separate lines.
Text Area (Rich)	Allows users to enter formatted text, add images and links. Up to 32,768 characters on separate lines.
Text (Encrypted)	Allows users to enter any combination of letters and numbers and store them in encrypted form.
URL	Allows users to enter any valid website address. When users click on the field, the URL will open in a separate browser window.

5. Select The Data type and then Click on next button.

6. Here i'm selecting Text data type.

7. Enter the details like this,
Field Label: It's your field display Name.
Length: Length of the field,means how many characters can accepts.
Field Name: The field name is used whenever referencing the field via the api.
Description: This is optional field,you can enter any description.
Help Text: This text displays on detail and edit pages when users hover over the Info icon next to this field.
                    it's use full to what data user enters.
Required: This field is required field every time save the record.
Unique: It's doesn't accepts duplicate values.
External ID: When importing Records to object you can use external IDs to prevent duplicate records                         from being created as a result of the import operation.
Default Value: We can set the default value for the field using formula expressions.
                       Fill all the details Then click on next.

8. Here give the security for field.Select the check boxes to do the visible,Read Only and both visible read only only to the profiles.after selection click on next.

9. It's for displaying field on object layout. If the field will not appear on any pages if you do not select a layout.after that click on save button.you done it.
10. You want to see it go to-->setup-->create--->select object-->scroll down to custom fields and relation ships section you found it.