WhatsApp is an app that you can use with androids and iOS devices. You are able to chat, video, call, post ‘stories’, and it is FREE! You can even download it to your laptop and tablets, but it must be connected to a phone/phone number first.
WhatsApp can backup to your iCloud or Google Drive based on your preferences.
You can set custom notifications for individual contacts or a general setting for all contacts.
You are also able to change chat backgrounds to colors or images.
The app allows you to mark important messages.
You can set how much data is used while using the app by controlling automatic downloads of photos, audio, video, and documents.