Signal looks and works a lot like other basic messaging apps, so it’s easy to get started. It’s especially convenient if you have friends and family overseas because, like iMessage and WhatsApp, Signal lets you sidestep expensive international SMS fees. It also supports voice and video calls, so you can cut out Skype and FaceTime. You can send pictures, videos, and documents.
It’s available on iOS, Android, and desktop.
Plenty of apps have all that stuff. The thing that actually makes Signal superior is that it’s easy to ensure that the contents of every chat remain private and unable to be read by anyone else.