Additional cards on debit cards aren't a standardized service across all banks.
Key points
If your bank offers them, ask if the card is directly linked to the same account, if it has its own spending limit or the same as the original card, and who is responsible for transactions.
If you need a card for someone else, make sure the product is designed for that purpose instead of sharing your card or PIN, which is an unsafe practice.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.