Short answers, pulled from the story.
A folk dance is a dance that reflects the life of the people of a certain country or region. It is typically performed at social gatherings by people with little or no professional training, often accompanied by traditional or folk music, and is significantly bound by inherited tradition.
Ritual dances, or dances of ritual origin, are not considered folk dances. They are usually called religious dances because of their purpose, which sets them apart from folk dances that originate as participatory social activities.
Hip hop and other modern street styles evolve spontaneously within communities, but the term folk dance is generally not applied to them. They are more commonly referred to as street dances or vernacular dances, because folk dance is reserved for forms significantly bound by tradition.
Balfolk refers to social dance events featuring live folk-inspired music, popular primarily in Western and Central Europe. The movement originated during the folk revival of the 1970s and has grown since around 2000, featuring partner dances such as the schottische, polka, mazurka, and waltz.
New dancers typically learn folk dances through informal means, by observing, imitating, and receiving assistance from more experienced participants. They generally do not learn through formal instruction.
Examples include the Dabke of the Levant, Bhangra and Giddha from Punjab, Garba from Gujarat, Bon Odori in Japan, Tinikling of the Philippines, the cueca of South America, the hula of Hawaii, and the haka of New Zealand. Folk dance traditions exist across Europe, Asia, Africa, the Americas, and Oceania.