What's the difference been molecular shape and molecular geometry?

There is no difference between molecular shape and . They both mean the same thing.

However, there is a difference between molecular shape and electron geometry.

The Lewis structures of CH₄, NH₃, and H₂O are:

They all have four electron pairs about the central atom, so they are all sp³ hybridized.

Their orbitals all point about 109° towards the corners of a tetrahedron. We say that the electron geometry is tetrahedral.

Note that CH₄ has no lone pairs, NH₃ has one lone pair, and H₂O has two lone pairs. The molecular geometry considers only the arrangement of the bonds. It ignores the lone pairs.

In CH₄, the C-H bonds all point towards the corners of a tetrahedron at angles of 109.5°. We say that the molecular geometry and the electron geometry of CH₄ are each tetrahedral.

In NH₃, the three N-H bonds point towards three of the corners of a tetrahedron. The molecule looks like a three-legged stool sitting on the floor with the N atom as a seat on the top. It is like a pyramid with a triangular base.

We say that the molecular shape of NH₃ is trigonal pyramidal, but its electron geometry is still tetrahedral.

In H₂O, the two O-H bonds point towards two of the corners of a tetrahedron. The molecule looks like an obtuse angle.

We say that the molecular shape of H₂O is bent, but its electron geometry is still tetrahedral.