The companies and corporations listed here are the most powerful, and the biggest actors in their respective fields. It can be safely assumed that your character knows about all of the ones originating from your home-planet and probably quite a few of the others as well.
Everything found in this particular list is a massive conglomerate, striving to achieve monopoly in their respective field and employing millions, possibly even billions of people and machines. These "megacorps" are so powerful that they can pretty much ignore local laws, often possess their own heavily armed security forces and many even hold "sovereign" territory, in which they pretty much act as outright governments. They often exercise a large degree of control over their employees, taking the idea of "corporate culture" to an extreme.