Gouache paint is opaque watercolour, it contains opacifiers such as chalk so that it appears opaque. Some painters will use it alongside watercolour and often refer to it as 'body colour', others use it as a medium in its own right. It is re-wettable and reworkable.
Acrylic gouache is very fluid acrylic colour. It dries waterproof. it is usually matte or semi-matte in its appearance. Acrylic Gouache is used in fine arts, whenever a totally flat, opaque surface is required, and as a poster paint in graphic arts, design and illustration. The colours have an ideal consistency for use with stencils and silk-screens. Painting tools are cleaned with water or alcohol if the paint has dried.
Traditional gouache, effectively being opaque watercolour, will only adhere to surfaces that possess a degree of absorbency, such as paper. You could prepare non absorbent surfaces by priming with watercolour ground to make them suitable for gouache painting. Acrylic gouache is a form of acrylic paint and so like most acrylic paints will adhere to most surfaces including metal, wood, paper and plastic.