Climbing out of crib

So I think my boy is almost able to climb out of his crib. We put a baby gate in his doorway at night just in case (he is upstairs) my question is..his crib turn into a normal bed- what’s the difference between a toddler bed and taking a long side off of his crib and putting the side rail so he doesn’t fall out? Preference? Also/ how do you keep them in bed?! My friend said her son just started doing this and they have had him in bed with them for the first time ever because he won’t stay in bed