Good ol' boy is an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 slang

Slang

Slang is the use of informal words and expressions that are not considered standard in the speaker's language or dialect but are considered more acceptable when used socially. Slang is often to be found in areas of the lexicon that refer to things considered taboo...

 term that can have both positive and negative meanings, depending on context and usage.

The term can be used for well socialized men who live in rural

Rural

Rural areas or the country or countryside are areas that are not urbanized, though when large areas are described, country towns and smaller cities will be included. They have a low population density, and typically much of the land is devoted to agriculture...

 and generally Southern areas. If a man is humble and well thought of, he can be referred to as a "good old boy", regardless of his age. It is commonly applied to men with a family or generational wealth or prestige, or overall moral behavior.

It can be used as a pejorative term, referring to someone who engages in cronyism

Cronyism

Cronyism is partiality to long-standing friends, especially by appointing them to positions of authority, regardless of their qualifications. Hence, cronyism is contrary in practice and principle to meritocracy....

 among men who have known each other for a long period of time. Collectively these people are referred to using the slang term, good ol' boy network

Good ol' boy network

Good ol' boy network, or "Good old boys", describes a system of social networking/cronyism perceived to exist among communities and social strata. These networks are perceived to be located throughout the world...

.