Understanding VAT Calculation

Hello everyone.

I have a question regarding VAT calculation that I'm hoping someone here can help me with. I've been trying to figure out how to calculate VAT for my business transactions, but I'm a bit confused about the process. Could someone please explain the steps involved in calculating VAT on this site https://southafricanvatcalculator.co.za/? Specifically, I'm unsure about which items are subject to VAT and at what rate. Any clarification or guidance would be greatly appreciated.

Thank you in advance for your assistance!