Firstly, the currency is certainly not always $’s in the exam!!!.
Netting is using the receipt of one currency to make part payment in the same currency, so only the net amount is converted and it is therefore only the net amount that is at risk.
Matching is where you have ongoing receipts in a foreign currency (that are therefore subject to risk) and create an ongoing expense in the same currency (which effectively cancels out the risk).
Both are explained (with examples) in my free lectures.
The lectures are a complete free course for Paper FM and cover everything needed to be able to pass the exam well.