The Web Customer field is commonly enabled to designate Customers as part of a group (of Web Customers) and may be used when filtering on reports or when exporting the Customer database.
Enabling the Web Customer flag has no affect on Customer pricing or on how their Sales Transactions are completed.
The Web Customer field may also be used in Label Manager when printing labels. Mailing labels for only Web Customer customers may be printed when offering coupons or promotional sales events.
See:
Customer Database - More Data Screen Fields