A regular tetrahedron has exactly two nets. There are three ways to join four equilateral triangles edge to edge, but only two of them fold up into a tetrahedron: the large triangle, an equilateral triangle of side 2 divided into four, and the strip, four triangles joined in a row into a parallelogram.
In the large triangle the middle triangle stays flat and the three corner triangles lift to close the solid. The strip folds from one end to the other. In both, each of the four triangles becomes one face of the solid, so turning on the numbers in the display panel lets you follow where every face ends up.
The dihedral angle of a regular tetrahedron is arccos(1/3), about 70.53 degrees. Folding a net back means lifting through the supplement of that, so each crease closes through about 109.47 degrees. That is deeper than the 90 degrees of a cube, which is why a tetrahedron looks different on the way open.