Groups enables you to decide which companies' delegates can or cannot request meetings with other Groups (including their own), and which Custom fields they can use to build their profiles.
For example, Group A might consist of 'buyers' looking for suitable suppliers for their business. Group B would be 'suppliers' who are selling their products. You can configure the system so that the suppliers can set up a sales profile with products, business sector target, etc, and only buyers can request meetings. In this scenario, buyers would screen suppliers on the basis of their custom profiles, and then send meeting requests to their preferred targets.
To learn more about creating Groups, visit this article.