WhatsApp is a free messaging app that lets users send and receive text, photos, videos, and more. It's available on Android and iPhone smartphones, as well as Mac and Windows PCs. 

Features 

Free calling: Make free calls to other users around the world

Group chats: Easily start conversations with multiple people

Privacy: Use end-to-end encryption and privacy controls

Location sharing: Share your location in real time

Voice and video: Send voice and video messages

Documents: Send documents

Stickers and GIFs: Express yourself with stickers and GIFs

How to use WhatsApp 

You need a compatible smartphone or tablet with a SIM card

You need an internet connection

You need a phone number

WhatsApp Business

There's also a free WhatsApp Business app that lets businesses reach their customers. 

WhatsApp and SMS

WhatsApp started as an alternative to SMS, but it's more conversation-focused. SMS is often used for one-way communication.