Bitcoin exchanges are a simple way to buy bitcoin with rupiah. They are especially suitable for beginners as most of them offer a user-friendly interface, customer support, and other features. In turn, you pay a fee for the services. However, they ask for KYC, which could be a privacy risk, and it's not recommended to store your bitcoin on an exchange. Why? Because if you don't hold the keys, the bitcoin isn't really yours (custody vs. self-custody).