These are called collective plurals ("собирательные числительные").

1. Usually it is considered that "collective" plurals двое, трое, четверо and so on are use only for nouns of masculine and common gender. "пятеро женщин" is incorrect, though natives sometimes make such mistake (as it is not clear why you should not do so: probably, etymologically it was not used for feminine). These numerals are normally used with nouns denoting people, those or masuline and common gender. Also used with люди, ребята, дети, лица.

2. The difference is that it is a "collective" plural, so it more closely views people as a single group. A shade of meaning, I'd say. The difference in use is that, first, you rarely go beyond "семеро" and, second, oblique cases of collective plurals are really rare. So while you may see something like "С теми двоими мужчинами что-то не так" ("Something's wrong with these two men") once in a while, it is by no means a natural construction, and you would sound non-native should you use it often (fortunately, it look so convoluted that you are unlikely to use it often :))

3. The one additional use you should remember is for pluralia tantum nouns: those that are used only in plural (like English "scissors", "pants"): штаны, ворота, ножницы, сутки, часы. Remember, in Russian when you need a Nominative-like form of number+noun for 1,2,3,4, you need Nom/Gen singular? But those nouns do not have singular! So instead you use:

• одни ножницы
• двое/трое/четверо ножниц And use normal numerals in oblique cases. It becomes convoluted with numbers like 22,23,54 and so on. Believe it or not, they just cannot be used with such nouns. Though you may always say something like "22 items of scissors" (22 штуки ножниц) or just "more that twenty scissors", which is more useful anyway. The whole problem probably originated in the fact that people do not often use large numbers in colloquial speech.

These are called collective plurals ("собирательные числительные").

1. Usually it is considered that "collective" plurals двое, трое, четверо and so on are used only for nouns of masculine and common gender. "пятеро женщин" is incorrect, though natives sometimes make such mistake (as it is not clear why you should not do so: probably, etymologically it was not used for feminine). These numerals are normally used with nouns denoting people, those or masuline and common gender. Also used with люди, ребята, дети, лица.

2. The difference is that it is a "collective" plural, so it more closely views people as a single group. A shade of meaning, I'd say. The difference in use is that, first, you rarely go beyond "семеро" and, second, oblique cases of collective plurals are really rare. So while you may see something like "С теми двоими мужчинами что-то не так" ("Something's wrong with these two men") once in a while, it is by no means a natural construction, and you would sound non-native should you use it often (fortunately, it look so convoluted that you are unlikely to use it often :))

3. The one additional use you should remember is for pluralia tantum nouns: those that are used only in plural (like English "scissors", "pants"): штаны, ворота, ножницы, сутки, часы. Remember, in Russian when you need a Nominative-like form of number+noun for 1,2,3,4, you need Nom/Gen singular? But those nouns do not have singular! So instead you use:

• одни ножницы
• двое/трое/четверо ножниц, also пятеро, шестеро ножниц. Some sources say that "двое/трое/четверо" should not be used with such nouns, some say nothing like that. And use normal numerals in oblique cases. It becomes convoluted with numbers like 22,23,54 and so on. Believe it or not, they just cannot be used with such nouns. Though you may always say something like "22 items of scissors" (22 штуки ножниц) or just "more that twenty scissors", which is more useful anyway. The whole problem probably originated in the fact that people do not often use large numbers in colloquial speech.