gun vaachak tell about the physical description about something.
For ex: palak sundar hai.
sankhya vachak tells about the quantity of something.
For ex: palak ne 2 aam khaae.
parimaan vaachak are also like sankhya vaachak but they don't tell the exact quantity.
For ex: 2 litre doodh chahiye.
(IDK about sanket vaachak!! u should check the book maybe...)