There are 2 company fields that are part of the original configuration of VisionProject, "Reporter Company" and "Company".
The "reporter company"-field is normally the field that you should use. It is a field that is automatically set to the company (and/or department) where the Reporter person works, i.e. the end-user or customer contact person.
The reporter company field is powerful to use for searching and finding all issues reported from one company and also for creating filters. By default, this field is hidden when creating an issue, but it is visible when editing it.
The "company"-field, on the other hand is a generic field containing all companies set up in VisionProject. It has no connection to any other field and can be used for different purposes where the normal reporter-company might not be enough. By using this field on your issue, you can tie the issue to multiple companies so it will show up in the issues tab on the company.
One example of a combination between the two fields could be when the project is a helpdesk-project. The person reporting the issue will then work on the reporter company (company and/or department), and the company could be the company responsible for fixing the issue, or the solution provider. For example, if your internet connection is down, you might want to put the Internet Provider in the Company-field. This way you can easily see all issues related to a company by filtering on this, or even going to the "General" --> "Companies" and see it on the issues tab for that company.
Please note that under normal circumstances it is not recommended that the company field is used, and you should use the reporter company.