Just as stocks and shares have become synonymous, so too the terms company and group have become interchangeable.
Strictly speaking, a company is one single business entity while a group is a group of companies all under the same ownership.
In a group, there will be a parent company that owns the various parts of the empire, which are the subsidiary companies kept separate for administrative convenience because they are into different lines of business or they operate in different countries.
Sometimes the parent company produces goods and services as well. In some cases the parent company does little itself and simply exists as the umbrella under which the subsidiaries ...