RingCentral is a US cloud communications company offering business phone, messaging, video meetings and contact-centre software, with AI features for distributed teams.
Zoom is a US communications company known for its video meeting platform, also offering team chat, phone, webinars, events and AI companion tools for remote and hybrid work.
Slack is a US workplace messaging platform, owned by Salesforce, organising team conversations into channels and integrating thousands of apps, huddles and workflow automation.