After neumorphism's same-tone shadows drew accessibility criticism for low contrast, claymorphism emerged as a compromise — keep the soft, dimensional feel but raise contrast substantially. Pastel colors, very large border-radius (near capsule/blob shapes), and two stacked shadows — an outer soft glow and an inner light highlight — combine into a "puffed up and squeezable" look.
It shows up often on buttons and icon badges, and pairs well with illustration on onboarding screens and app icons. The build is just several layered box-shadow values (an outer soft shadow, an inner light highlight, an inner dark shadow) over a pastel gradient — pure CSS, nothing exotic.
Apply it to too many elements and the whole screen turns soft and mushy, blurring hierarchy. It's safer as an accent — a few cards, an icon, one hero illustration.