In design, especially in architecture and industrial design, form follows function. On the surface, the word might seems a little technical, but it is as simple as it gets.
So here, the function of a certain building for instance determines the form. The aesthetic form depends on the purpose of the building constructed. But the form is actually just part of the design. What people sees more is the function. What's the use of something if it just have the form but no function? so here, it is clear that function is more important than form.
from there, we can understand the meaning of Form is Function, Function is More.