If Gmail is controlled by SMTP server, Which server is Used for Facebook????

SMTP(Simple Mail Transfer Protocol) is a protocol that is used for email transmission. To find info about Facebook's server, it is built with PHP, so we can say it uses PHP Server. Talking about the protocol, Facebook uses HTTPS(HyperText Transfer Protocol Secured). So, relating with that gmail we can say Facebook uses HTTPS Server.

Apollo-Roboto I asked about Server Not for Query Language..... There is no collocation in your Answer

facebook and pretty much all other social media stores their data on sql/nosql databases.