There are two types of succession Primary and Secondary. Primary succession is when a large area of barren rock is slowly transformed into an ecosystem. This process starts with a pioneer species, which is a type of plant that thrives in places other species prefer do not. Anyways, these pioneer plants use chemicals in their roots to break down the barren rock and create sediments. After these plants die, their remains are broken down by decomposers, and creates humus to make soil. This soil is populated by different phases of plants. Usually starting with small plants like shrubs, and then going to softwood trees that are later replaced by softwood trees.
Secondary succession is pretty much the same process, but it starts when a pre-existing ecosystem like a forest is destroyed by a great force like a wild fire. It also already has fertile soil, so different kinds of pioneer species come first.

What is Succession?