The first stage in the information of coal is?

Rotting vegetation is overlaid by more rotting vegetation or other material.

This is compressed by the mass above and form peat.

Compression of the peat continues and form lignite (brown coal)

Compression continues on the lignite to form coal (clack shiny rock)

Compression may continue to form anthracite , the hardest form of coal .

NB with each compression watert/moisture is expelled, so coal and anthracite are very dry.