The Default Value property of a field allows you to provide a default value for the field. When you set a default value of a field, users will see that value by default whenever they create a new entry. However, you do have the provision to change this value while creating an entry.
The advantage of using this property is when you don’t want to enter constant data every time while creating multiple entries, the provided default value gets applied to the field it's assigned to.
For example, for a Location (Multi Line Textbox) field you won’t need to enter the same data every time you create an entry. Instead, you can use the Default Value property and enter the data of the Location field while configuring the content type.
Note: If you choose to modify the default value of a field after creating some entries for the content type, the updated value will only apply to new entries created thereafter, while the existing entries will retain their original values.