Man is an ambiguous word from Germany languages that may or may not refer to adult male individuals either by gender identity or by biology or may be used to refer to all of Humanity, including people who are not male either by gender identity or by biology. The reason for the ambiguity seems to be due to maleness being considered the "default" or "ideal" form of a human being and therefore synonymous with the idea of Humanity as a whole; an idea that, strangely enough, exists even among so called "woke" individuals considering the popularity of "generic masculine" terms in woke communities, for example, using "guys" to refer to people who are not male either by biology or by gender identity.
"Man," when used to refer to gender or biological sex, is a term used for adults, and corresponds to the terms boy (for children), male (adjective) and masculinity.
Identification and Relation to Sex
Children who are born with penises and testes are often raised with the expectation that they will identify as men, although intersex children may also be assigned to this identity while possessing some but not all of the above characteristics, Men may be cisgender (assigned male at birth and identifying as male) or transgender (assigned female at birth, yet identifying as male).
Identifying as a man is often associated with male sex characteristics such as a penis, testes, narrow hips, a prominent Adam's apple and a low-pitched voice, as well as a masculine gender expression and gender role, but these are not necessary, and it is still possible to identify as a man without them.
Androcentrism is the treatment of maleness as the "ideal" or "default" in humans and may be seen in many aspects of life from language, culture and many other things: https://tvtropes.org/pmwiki/pmwiki.php/Main/MenAreGenericWomenAreSpecial
In recent times, significant efforts have been done to combat androcentrism with a famous recent example being Justin Trudeau rightfully correcting a woman for the use of an androcentric term over a more politically correct one: https://www.youtube.com/watch?v=ItsGW1Nlm3c