CFW = Custom Firmware, and no such thing on the PS Vita as of yet.
eCFW = "Emulated" CFW, if I recall correctly. It refers to Custom Firmware running on the embedded PSP Mode of the system. This kind of CFW is launched using an exploitable PSN game. eCFW requires a kernel-level exploit, so it's not always available.
VHBL = Vita Half-Byte Loader. VHBL is an application used for launching homebrew, it's booted much like eCFW, but does not require a kernel-level exploit, userland exploits are good enough.
In short, PSP Mode has been hacked and occasionally hackers release new exploits for it. PSVita Mode has not been hacked and we're nowhere near hacking it. If you're looking for the latest PSP Mode releases, head to Wololo.net and register at their forums - they usually release the titles prior to official announcements.