The form of a work is its shape, including its volume or perceived volume. A 3 dimentional artwork has depth as well as width and height. Three-dimensional form is the basis of sculpture. 2 dimentional artwork can achieve the illusion of form with the use of perspective and shading or modelling techniques.
Texture is used to describe how something feels or looks. Her hair was smooth. Smooth is a texture, same as bumpy, hard, light, clear, rough and many, many, many more.