S4B meaning in Computing ?

Skype for Business (formerly Microsoft Lync and Office Communicator) was an enterprise software application for instant messaging and videotelephony developed by Microsoft as part of the Microsoft Office suite. It is designed for use with the on-premises Skype for Business Server software, and a software as a service version offered as part of Office 365. It supports text, audio, and video chat, and integrates with Microsoft Office components such as Exchange and SharePoint.

In 2015, the software was rebranded from Lync to Skype for Business, co-branding it with the Microsoft-owned consumer messaging platform Skype (which had begun to integrate with Lync in 2013).

In September 2017, Microsoft announced that it would phase out Skype for Business in favor of Microsoft Teams, a new cloud-based collaboration platform. Support for Skype for Business Online ended in July 2021, and Skype for Business Server 2019 will receive extended support through October 14, 2025.