What it means
Among the eight chara karakas, the Putrakaraka is whichever planet holds the sixth-highest degree in its sign. Jaimini reads it as the significator of children, and by extension of anything brought into being and then allowed to become its own thing - a body of work as much as a family.
How it is read
Like every chara karaka it is chart-specific rather than fixed: any graha can take the role, and it shifts between charts. It is read together with the fifth house and with Jupiter, the natural karaka for children, rather than instead of them - the chara karaka answers a Jaimini question, the fifth house a Parashari one.
What to watch for
A caution worth stating plainly: no single significator determines whether someone has children. The Putrakaraka describes a theme, and traditions differ on whether the sixth-ranked planet or the fifth house carries more weight. Read it as one input among several, not as a verdict.