Phosphate fertilizer: calcium magnesium phosphate, calcium superphosphate (common superphosphate), heavy calcium and phosphate rock powder.
Potassium fertilizer: potassium chloride and potassium sulfate.
Compound fertilizer: refers to chemical fertilizer containing two or more N\P\K elements. Including monoammonium (monoammonium phosphate), diammonium, potassium nitrate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate and those ternary and binary compound fertilizers sold in the market (there are many kinds, such as 15- 15 ternary compound fertilizers of hydro).
The essence of chemical fertilizer is mineral nutrients that plants can absorb and utilize (except urea), so any substance containing the above nutrients can be called fertilizer.