What is a Difference between default paging and custom paging?

• Default paging—Can be implemented by just checking the Enable Paging option in the data Web control's smart tag. However, whenever viewing a page of data, the ObjectDataSource retrieves all of the records, even though only a subset of them is displayed in the page.
• Custom paging—Improves the performance of default paging by retrieving only those records from the database that must be displayed for the particular page of data requested by the user. However, custom paging involves a bit more effort to implement than default paging.