it's pretty much creating an accurate miniatrue replica of a certain area in the world. For example copying a sout east asian biotope would involve mimicing the water conditions of the swamps in SE asian and having an abundance of driftwood. the plants and animals would all be species that could be found naturally in that area, such as java fern and java moss for plants and for stocking using loaches, danios, rasboras, barbs, gourami, etc...