I'm not convinced this is an appropriate question, but giving the benefit of the doubt and since the OP is probably not a geometer...

The flat torus cannot be embedded in $\mathbb{R}^3$ isometrically. Since the torus is compact, any embedded torus lies in the interior of some sphere centered at the origin. Decrease the radius of the sphere until it just touches the torus for the first time. At the point of contact, the curvature of the torus agrees with that of the sphere, and is hence positive.

I'm not convinced this is an appropriate question, but giving the benefit of the doubt and since the OP is probably not a geometer...

The flat torus cannot be smoothly embedded in $\mathbb{R}^3$ isometrically. Since the torus is compact, any embedded torus lies in the interior of some sphere centered at the origin. Decrease the radius of the sphere until it just touches the torus for the first time. At the point of contact, the curvature of the torus agrees with that of the sphere, and is hence positive.