Once you add a contact in Aptter you can add his position and company he works for. If a company exists it will be shown while typing in the company field, or it will be automatically created if it does not exist.
In both scenarios the contact will be linked with the company.
When in company view, by clicking “people” you can see all contacts related with the company or search another one to relate with.
When in contact view, by clicking “links” you can see all contacts or companies related with it or search another one to link with.