Last survivor of the doomed planet Krypton, the infant Kal-El was rocketed to Earth and crash-landed in Kansas, where he was found and raised by Jonathan and Martha Kent. Eventually, he grew up, moved to Metropolis, made his debut as Superman, met Lois Lane, got a job working for Perry White with Lois and photographer Jimmy Olson, and tangled with Lex Luthor. While working at the Daily Planet, Clark courted Lois. They started dating and eventually got married.
With me so far? OK, this is where it gets complicated: Lois and Clark were visiting Gotham when the city was abducted and taken to an alien world, where it was sealed off for a year. During that year, Lois became pregnant. During the cataclysmic events at the end of that year, she gave birth to their son, Jonathan Kent. Gotham was sent back where it came from, but they volunteered to stay behind to avert a much larger crisis, after which they landed on the prime Earth at the dawn of the modern age of heroes. They have been living there under assumed names ever since, raising their son and working behind the scenes to make the world a better place.
Now, there are obviously more details to it than that. Some of those details may become important later on, such as Superman's death and return to life; when they do, further elaboration can be provided as needed. Other details are unlikely to ever see the light of day again and can safely be ignored: we can forget Grounded.
Depends what details are relevant to the story where the blurb is being placed. In a story where the audience is assumed to know the essentials of Superman's backstory and merely need to know what's different here, “Refugee from a lost timeline, Clark and his wife Lois have settled on this world to raise their son, Jonathan.”