In Skype for Business, groups are collections of contacts that you create so you can see several contacts in your display at a glance or communicate with them all at the same time. You decide what groups you need and who will belong to each one. Please note that in the latest version of Office 365 on the web, Skype has been integrated into the Teams app.
1. In the Skype main window, in your Contacts view, click the Add a contact
then click Create a New Group
2. In the space that now opens up at the bottom of the window, type over the phrase New Group to give your group a descriptive name.
In the Skype main window, in your Contact list, right-click the heading for the group you want to delete, then click Delete Group on the drop-down list. (You can also rename a group, or change the order in which your groups are displayed, from this same drop-down list.)