What does ecological succession explain?

is the gradual process by which ecosystems change and develop over time. Nothing remains the same and habitats are constantly changing.
A bare patch of land will not stay bare. It will rapidly be colonised by a variety of plants. In the process of succession the present in an area will gradually change.
Each species is adapted to thrive and compete best against other species under a very specific set of environmental conditions. If these conditions change , then the existing species will be replaced by a new set of species which are better adapted to the new condition.
Succession takes place because through the process of living , growing and reproducing, organisms interact with and affect the environment within an area , gradually changing it.
Succession is directional. Different stages is a particular habitat succession, can usually be accurately predicted. Succession will not go any further than the climax community.
Succession occurs on many different timescales, ranging from a few days to hundreds of years.