Doctor, XH, ZH, etc. They are all the material numbers of JST (Japan Standard Time Japan Press Terminal Manufacturing Co., Ltd.). Because JST is used the most, and many factories are imitating production, most of them have such codes, which is convenient for the selector to understand the matching with JST more conveniently.
Each code name is a series of products, and their biggest difference is that Pitch (commonly known as asphalt) is different.
Several common spacing:
FH0.5mm
Sh 1.0 mm
Gh1.25mm
Zh 1.5 mm
PH2.0mm mm
EH/XH2.5/2.54mm (these two are actually the same)
3.96 mm high