what is scramjet?

scramjet is just like ramjet. the process of fuel combustion is almost the same with ramjet. just that scramjet combusted the fuel supersonically to increase the efficiency of combustion. the faster the combust it's fuel, the faster the jet goes. sr-71 blackbird the fastest jet in history reach up to mach 3.4 using ramjet. the x-30 research gave up to mach 17. awesome didn't they?