White label is when one company delivers the service and someone else's brand sits on the front. Here that means the panel engine, servers, updates and platform support stay with SMMPanelRent, while a customer arriving to place an order sees only your site, your name and your colours.
For the business this solves something concrete. A panel under your own brand reads as a service in its own right rather than as resale: you can build a reputation on it, advertise your domain and accumulate repeat customers. If the address led to somebody else's platform, every unit of ad spend would be building their recognition instead of yours.
There is a second benefit: the brand does not tie you to one supplier. The catalogue and provider APIs are configured inside the panel, so when you change providers the address, the name and the customer base remain yours. What changes is what happens behind the counter, not the sign above it.