A man who is strong and masculine; meaning he pursues, defends, conquers and rules. Rather than being a "nice" guy, he's a "good" guy - not a pushover but strong in his convictions, values and resolve. (Example: someone who can "man up") This is not dependant on his socio-economic status, but rather his willingness to embrace his God-given masculinity.
A lot of women like a man's man; because they are strong and offer something different and very valuable to the experience of being female. When a woman finds a man's man who is a "good man" instead of a "nice man" she gets to have the perks of being with a "bad boy" -the strength, toughness and masculinity, without having to actually be with a bad boy. It's an ideal situation.