When creating a custom field in Salesforce, the first step is to select the appropriate data type for the field. There are many different field types which allow the storage of records of various data values such as numbers, dates, percentages, and so on. The following picture shows some of the fields and the rest of the blog describes the field types that are available.
An Auto Number field produces a unique number that is automatically incremented for each saved record. As such this is a read-only field where the maximum length is 30 characters of which 20 are reserved for further prefix or suffix text that you can specify.
A Checkbox allow your users to set or unset a value to mark the attribute as either true or false.
Salesforce provides a Currency field to specifically capture a money value. Here the Salesforce CRM application applies currency-related codes which are applied when working with that field record.
The Date field provides a way for your users to either pick a date from a pop-up calendar or to manually key the date. Your users can also enter the current date clicking on the date link positioned to the right of the field.
The Date/Time field provides a way for your users to either pick a date from a pop-up calendar or to manually key the date and the time of day. Your users can also enter the current date and time by clicking on the date and time link positioned to the right of the field. Here, the time of day includes A.M. or P.M. notation.
Email fields provide the facility to store an individual’s email address. The Salesforce CRM application provides a very robust method of verifying the correct format of e-mail addresses before they are allowed to be saved.
Formula fields provide a method to automatically calculate a value which is calculated from other fields or values stored within Salesforce CRM.
This field type forms a hierarchical lookup relationship between relevant objects. For the user hierarchical relationship, users can use a lookup field to associate one user with another For example, you can create a custom hierarchical relationship field to store each user’s direct manager.
The lookup relationship field creates a relationship between two records so you can associate them with each other. For example, opportunities have a lookup relationship with cases that enable you to associate a specific case with an opportunity. A lookup relationship has no effect on record deletion or security, plus the lookup field is not required in the object page layout.
Creates a parent-child type relationship between records where the master record controls certain behaviors of the detail record such as security and record deletion. Master-detail relationship fields can only be created on custom objects that relate to a standard object and not the other way. If the Master record is deleted then all detail records are also deleted. You can create up to two Master-detail relationship fields per custom object.
The Number data type can be used to enter any number with or without a decimal place (the number of decimal places can be specified) and saved as a real number with any leading zeros removed.
With Percent fields in Salesforce CRM, a percentage sign is automatically appended to the entered number. Fields values lose precision after 15 decimal places. If the decimal value is greater than 15 and a percent sign is added to the number, a runtime error occurs.
The Phone field allows the users in your organization to enter any telephone number.
The Picklist field allows users to choose a value from a set of pre-defined text values. The maximum length of the text values is 255 characters.
The Picklist (Multi-select) field allows users to choose more than one picklist value from a set of pre-defined text values. When saving and viewing, the data is stored as text along with semi-colons which are used to separate the individual picklist values.
A Roll-up Summary field (or RUS) is used to automatically display the summarized values of the related records. This can be a record count of related records or a calculation of the sum, minimum, or maximum value of the related records.
The Text field allows users to enter any combination of alphanumeric characters. The maximum length of the text value is 255 characters.
The Text (Encrypted) field allows users to enter any combination of alphanumeric characters. The text is then stored in an encrypted form (this data type is available by request to Salesforce support). The maximum length of the text value is 255 characters. Encrypted fields are encrypted with 128-bit master keys and use the AES (Advanced Encryption Standard) algorithm.
The Text Area field allows users to enter alphanumeric characters on separate lines. The maximum length of the text value is 255 characters and a warning is displayed when the number is about to be reached (as shown in the screenshot above).
Text Area (Long)
The Text Area (Long) provides for the storage of up to 32,000 characters that display on separate lines similar to a Text Area field. However you can specify a lower maximum length of this field type from between 256 and 32,000 characters. This data type is not available for activities or products on opportunities. Only the first 254 characters in a rich-text area or a long-text area is displayed in a report.
Text Area (Rich)
Using the Text Area (Rich) data type your users are provided with text field with an embedded toolbar. This toolbar allows for the simple formatting the text and provides for the adding of images and URL web links.
The URL field allows users to enter a web link. When the web link is clicked the Salesforce CRM application opens a new browser window to show the web page.
Reference: Salesforce CRM: The Definitive Admin Handbook book and eBook