When we say that you know he's in love when he's willing to give it his all, that might have a number of definitions for different couples. In general, giving it your all means investing all of your emotions and energy into the relationship. Whether that takes the form of marriage, a home, babies, travelling, love letters, or something else really depends on the type of couple you are.
Basically, what we're trying to say is that you're 'all in', just like in card games. You're willing to risk everything on this one chance you have with your partner. If this is the case with your man, we're not even sure why you need to read this article! He's clearly crazy about you. We just hope that you're equally crazy about this lovely man, too.