TPU stands for “thermoplastic polyurethane”. While also technically a class of materials, TPU is the most common type of TPE and is on the more rigid side of flexible filaments, making it easier to print with.
Since the terms of TPE and TPU are often interchanged loosely, it’s worthwhile to set the record straight.
Both TPE and TPU are categories of material, but TPE is a wider classification for soft materials, while TPU tends to be the more rigid-flexible filament.
TPE has generally been available for many years. As far as printing material goes, it varies more with respect to part performance and ease of printing.
TPU, a specific type of TPE, established itself in the 3D printing market only in the last few years. Being easier to print than non-TPU TPEs, it’s become the go-to FDM flexible filament.