In the movie Star Trek: Wrath of Khan, what did Spock mean when he mind melded with McCoy and he told him to "remember"?
The basic plot of ST.III is to go over to the Genesis Planet and find Spock's body, return it to Vulcan and let the Vulcans do whatever magic it is they do to dead people. Only, in stead of Spock's body, they discover a young & horny "regenerated" Spock, first as a child, but he rapidly grows into a teen ager and falls for Lt. Saavik.
Eventually, the rapidly maturing Spock grows up to his approximate age at the time of death and the crew travel to Vulcan. What Spock wanted McCoy to "remember", apparently, was his catra or soul. Vulcan magic is such that they can reintroduce the catra into the now regenereated body of Spock.
And they lived happily ever after, until they have to go find some whales.