Slack is a proprietary business communication platform.
Discord is a VoIP, instant messaging and digital distribution platform.
Telegram is a cloud-based mobile and desktop messaging app with a focus on security and speed.
WhatsApp, is a cross-platform centralized instant messaging (IM) and voice-over-IP (VoIP) service.
Microsoft Teams is a proprietary business communication platform.
Facebook is an online social media and social networking service.
Instagram is a photo and video sharing social networking service.