Data communication transmits digital data other than voice (text, images, video, app data) over networks. On mobile phones, web browsing, SMS, app usage, email, and video calls all use data communication.
Mobile data uses packet switching, dividing data into small "packets" that don't monopolize the line, allowing many simultaneous users. Plans set monthly data caps ("X GB/month"), with speed throttling after exceeding limits.
The voice-data relationship has evolved. 3G couldn't handle simultaneous voice and data, but 4G VoLTE processes voice as data, enabling web browsing during calls. 5G delivers even higher capacity and lower latency for quality video calls and real-time remote operations.
Save data by using Wi-Fi, lowering video quality settings, restricting background app updates, and enabling data saver features. LINE call vs phone call explains differences between data-based and circuit-switched calls.