"HD" means high definition, which can be high-definition resolution, high-definition voice, high-definition calls, high-definition music, etc. Friends who like to listen to music will be familiar with it. When downloading music, you are often asked to choose whether it is high definition (HD). In addition, when watching videos, you can choose different resolutions such as "HD" and "FHD".

Extended information:

The mobile phone supports "VoLTE" high-definition voice/call function. VoLTE, which is the abbreviation of Voice over LTE, literally means voice on 4G (TD-LTE). It is China Mobile's 4G voice high-definition service.

It should be noted that although VoLTE uses a 4G network, the current call rates are still charged according to the length of the call, not the data traffic. This is where China Mobile is a "chicken thief", charging according to the call length. Communication fees are obviously more substantial than traffic fees.