To understand and comprehend many will argue are the same concepts. Yet, Tony Stark would tell them they are flat out wrong. He sees the difference every day.
Saying Tony Stark comprehends love would mean he did his research, digging to the deepest root of the simplistic word. However, he did not comprehend love, he only understands it. If asking him what love is he can rattle off any answer that many others have said. He is a genius, but even he has the limitations of his own. Tony Stark could not comprehend love.
Daddy issues piling higher than Mt Everest Tony Stark was never given true love. He'll give you a simple few who he thinks he's come close to loving, yet even those are lies that he hides behind. On a single hand, two fingers raise steadily. Tony Stark knew how to love. His love meant them loving everything that is not him. Each person touches the surface, discarding the broken man and uses him further.
People use him, and that's why he can not hold true love or emotions. His heart gone, replace with a machine for that was what he became. Yet, even he can fool himself sometimes. He gave a single woman his broken soul, allowing her to fix him. She too left him, finding him unfix-able. Pepper Potts tried her best, Tony can give her that.
He fools himself once more, Steve Rogers. A male that his father held in front of his true son. The model is everything Tony was not, giving his father the reason to lust after him. The recent swelling in Tony didn't last long. His parents killed in a robbery gone wrong left the broken man many see today.
Steve Rogers was there. He gave friendship and solace to the young billionaire. It was Steve who gave Tony to Pepper, pushed for their relationship could thrive. Until it died. Tony was left alone again. When Steve tells Tony he loves him the best Tony could muster is a small, "Really?"
Tony gave up on love long before he recognized it himself. Steve revives it with his gentle words and smiles.
Tony can't say he's in shock when Steve tells him their love is gone. Steve found another. The happy night ruined. Steve left not only Tony behind, but the small toddler, crying in his room.
Tony Stark, a genius, a billionaire, a playboy, never holding his tongue for anyone. Peter sees the change first, his surrogate father smiling at him. The young toddler smiles back, even as Tony bites his tongue and lies.
"Your father will be back. He's off taking pictures with other sweet kids like you."
Comprehending and Understanding completely opposites. Peter stark-rogers learns how to use both when he speaks of the father who abandoned him.