How high up is space?

How can we define the limits of space? Is it an infinite expanse that stretches beyond our comprehension, or is there a specific height that marks the end of space and the beginning of something else? When we send rockets and spacecraft into orbit, how far up do they go? And what happens to them when they reach the so-called "edge" of space? Is it a hard and fast boundary, or is it more of a gradual transition? What challenges do astronauts and engineers face when exploring the vastness of space, and how do they overcome them? Can we ever truly know the answer to the question, "How high up is space?