SalesForce has a powerful new feature called Communities. It allows you to invite users external to your organization (e.g. customers, partners, etc.) into your SalesForce Instance. This allows you to extend the reach of SalesForce well beyond your traditional CRM system. This means you could use SalesForce to help make data available for different user groups or have them contribute their own. This can be useful, especially for partners if you want them to add in details of the opportunities they are working on!
Of course, you have the usual control over what these other users can see in your SalesForce instance. But, you also have the ability to custom brand your community so it looks nothing like SalesForce (or it can look entirely like SalesForce depending on your use case/preferences). This means you could create something that looks completely like something you made just for your community users.
You have the ability, depending on the community type (e.g. Customer or Partner) to expose custom objects from your SalesForce instance. And, if you are using a Partner Community (which costs more), you can expose Accounts, Contacts, Opportunities and Libraries. With the Customer Community you can expose Cases. So, depending on what is needed you can find the one that is right for you.
When it comes to licensing this exciting solution SalesForce has two different license models. One is for a pool of logins (say 10,000 logins per month). This is useful if you are expecting traffic to your community, but aren’t sure which users specifically will make up that amount. Alliteratively, you can go with the Named User model which is similar to how SalesForce licenses their CRM itself - every user accessing it needs their own license.
There are many exciting ways you can use communities!