Ram disk is exactly what it sounds like, you create a virtual disk in your system ram, to emulate an SSD. If you have a HDD this works pretty decent to create a hybrid SSD cache to run programs through, but having an SSD, especially as the os/boot drive will show no gains and/or could actually slow down performance as an SSD has its own cache controller on board that isn't restricted by mobo buss like Sata speeds.
Basically, ram disk using an SSD is absolutely pointless, the only thing it's going to do is use up space in the system ram and the ram disk itself will only run at system ram speeds, regardless of whatever speed the SSD runs at. It was a decent idea back on 2012,before SSDs really took off and anyone with 8Gb of ram was good, or for server settings using massive amounts of ram with hdds used as common storage, but by today's standards, it's seriously outmoded.