Slack is currently one of the most popular multi-featured chat services out there. With Skype support the Slack messenger just got a little better once again.
Microsoft has created a little introductory page for Skype´s Slack integration which is handled by Slacks App management.
You can add the Slack App for Skype by clicking here and then confirming by selecting Authorize in the next step.
Then inside of Slack, Skype calls with all members can be initiated by typing /skype as a command. Anyone on your team then can join the call whether they have a Skype account or not. They can sign in as a guest, with a Microsoft account, or Skype Name.
Source: Microsoft