Sales Custom Fields
To add extra fields to the Sales module, go to the Settings>>Custom Fields>>Sales Custom Fields.
You need to specify which item it relates to: Lead, Opportunity, Account, Contact or Case. Then you need to set the Field Name, Alias Name, Data type, and Field Type.
Show in listing
If you check this box, the field will show up as a column in the Contacts List for the quick view. So you do not have to go to the Contact Summary page to see the custom field data.
Show in filter
If you want to make the new field filterable, you need to check this box. After that, you will be able to filter your Contacts based on this field as well.
This is the additional name of the new field that helps you to move data to other sections. For example, you have the custom field in Opportunity and in the Projects section. If the Alias name is the same for the custom fields in these sections, the custom fields data will also be moved to the Projects section when you Convert an Opportunity to a Project. So the Alias Name is needed when you convert items.
Here you specify what kind of information the new custom field carries: Date, Text, or Number.
The field types can be Text, Date Picker (if you have chosen Date as Data Type), Radio Button, CheckBox, Entity Dropdown, or Text Area where you can add longer text.
If you check this box, the field will be a mandatory one to fill in, so you will not be able to save the item without entering data into the custom field.