In order to take payments online you need an e-commerce enabled website and the services of a payment provider that is compatible with your website.
Payment Providers come in two different types either standalone or requiring a Merchant Bank Account.
These type of payment providers offer a complete standalone payment processing service with no merchant account required. Such a service is PayPal. These providers will usually take a percentage of the order value and payment processing fee. There may also be additional fees for paying funds into your bank account.
If you have an existing Merchant account or you are looking to take a large volume of transactions or high value orders then this type of Payment Provider may be the more suitable. With these payment providers you need a Merchant account with Online Payment enabled. The Payment Provider then provides the online payment processing service and the funds are deposited into your merchant account. These providers will usually charge a monthly fee for a fixed number of transactions and then a per transaction fixed fee for any other transactions. You will then also be charged by your merchant account for each transaction at its processing rate.
Whichever payment provider you choose to use it must also be compatible with your e-commerce website.