Credit is an inner value of payments on the website, with which client pay for services.
Credits can be purchased by packs with online transactions, received as bonus for activity on the website, received for completing tasks or granted by administration.
More details about this feature you can find here.
https://www.bridge-of-love.com/article-website_credits-1216.html
Also we recommend you to read this price list
https://www.bridge-of-love.com/article-how_much_it_costs-599.html