It features a classic, relaxed design suitable for both toddlers and young children. Here are the specific details of the style:

• Top: A short-sleeved, crewneck t-shirt.

• Bottom: Matching full-length jogger-style pants with an elastic waistband and a decorative drawstring.

• Pattern: An all-over  print 

• Fabric: It appears to be a soft, breathable cotton jersey or a cotton-spandex blend, which is standard for high-quality children’s sleepwear.

This type of set is often referred to as "unisex loungewear" or a "t-shirt and jogger PJ set."