How company context works
A single user can belong to more than one company, but the app is always operating inside one active company at a time. The company switcher in the sidebar changes the active company and reloads the app in that context from the Dashboard or anywhere else in the app.
Who gets multi-company access
Multi-company access is a Pro-plan feature. On Standard, each account is scoped to a single company. Pro accounts can belong to multiple companies and switch between them without signing out.