With cut and sew, you choose the fit, fabric, weight, color, trims and construction details: a boxier body, a custom neck rib, a particular fleece, a hidden pocket. A pattern maker turns the design into pattern pieces, fabric is sourced and cut, and a factory sews the garments, usually after several sample rounds.
That control brings more steps. Cut and sew needs a tech pack, samples and fit approvals, fabric with its own minimums and lead times, and a size range that has been graded. Minimum quantities per style and color are usually higher than for decorated blanks, and timelines are longer.
Brands often move to cut and sew once they have a proven product and want a fit or fabric no blank offers. Before then, relabeled premium blanks can deliver much of the look. See blanks vs cut and sew and MOQs and timelines.