Creator revenue is the total monies you earn from the sale of your published material. Creator revenue includes Royalties and Other Revenue.
When a creator buys a Lulu distribution service and their material is assigned a Lulu-owned ISBN, Lulu becomes the publisher of record and all earnings are regarded as royalties for that material, regardless of delivery format. The creator revenue generated by sales of material with a Lulu-owned ISBN meets the true and legal definition of a royalty. Royalties are reported to the IRS and are subject to withholding according to United States of America tax laws.
For more information about tax withholding, see: Royalties and Tax Withholding
If your book does not have a Lulu-owned ISBN, then your earnings are not royalties but simply Other Revenue, which is the amount of money you make on each sale of your published material. Other revenues are not subject to withholding and are not reported to the IRS.