A medium is a composition of different solutions and steps that are required to cultivate defined microorganisms.
Solutions are the building blocks of media. One solution can be used in many media (e.g. Trace element solution).
Ingredients can be either chemical compounds (e.g. Glucose or MgSO4) or complex substances (e.g. Yeast extract).
BacMedia also includes a list of all microorganisms that grow on the media.