Clans support is directed towards the very competitive side of StarCraft 2, while Groups will cater to the more casual players circle.
On their website Blizzard has outlined the details regarding how Groups will actually work. To start off both Clans and Groups will have similar initial features that includes their own channel, news feed and rosters.
The difference lies in the number of recruitments. Groups will be able to accept almost limitless number of members while clans are restricted to 50. Additionally players can join up to 20 groups per character but only one clan per character.
The Groups feature is a way for you to meet and interact with other StarCraft 2 players who share common interests. Accordingly, when you create a Group, you’ll select a category that best describes the type of Group you are creating.
These categories include topics such as BarCraft for Groups that are interested in finding and keeping in touch with friends they’ve made at BarCraft events, Strategy and Coaching for Groups that are looking to share their favorite strategies and helping others improve their play, and many more.
StarCraft 2: Heart of the Swarm will be released for PC and Mac on March 12, 2013.