This is what we call a glossary of terms.
A glossary is like a simple explanation of anything that might be complicated, such as a specific medical word that may not understand.
The glossary will hopefully answer you as to what that specific word means.
Man Boobs is slang for Gynecomatia.
Gynecomastia is the swelling of the male chest leading in the male chest starting to look like a woman's.
Bitch Tits is a very rude and offensive way of saying a man has swelling of the chest area.
Gynexin is the leading male chest fat reduction treatment other than surgery.
Lactating is when a man produces milk in the same way a woman does to feed her baby.