"I need space" simply means I've found someone else I'm interested in, but if it doesn't work out as expected I'll be back.
Never go back or allow a partner come back to you after the "I need space" talk...break up the very moment they say it, you're worth more than that. You're worth more than being an option in a person's life.

More or less like a tentative invitation to an open relationship

"I need a space" in most times is a freedom ticket to get wilder, naughtier, baraje, and bitchy exploration.