Payment gateway (PGs) service providers are 3rd party companies which deal into processing online transactions on your online store. We at ShopGoOn, technically integrate these PGs into your website. Further you can signup with them (one or few of them), on their respective company website to start getting services from them.
For example, If you wish to activate ccaveue, visit www.ccavenue.com and sign up for an account. You can sign up for such free or paid account. Put account details in your admin panel to set it enable. You are ready to accept online payments via credit card, debit card, net banking etc.. Money flows from customer to your ccavenue account to your bank account. You will be charged for per transaction fees (normally 2-3%) by payment gateway company. You need to accept their terms and conditions for such services. You are free to choose any of them. Also, you can enable/disable them by any time.