I've never really heard of "hard reset" before for a cell phone.
If by "Hard Reset" you really mean Hard Reboot or cold boot it would be... power off/on.. or use the reboot option in an app like Quick Boot (reboot)
A "soft reboot" is where you press/hold the power button on the X, and from the pop-up say "restart" which closes apps and stops a few services and restarts (kind of like what happens in windows when explorer.exe crashes). The device doesn't completely shut down or shut off. It more or less just restarts some services.
If it really is "hard reset" then please supply the context or where it was used so we can better understand and explain it.