I used to have the biggest collection of Barbie dolls when I was a wee lad.
what type of doll is Barbie dolls?
Barbies are a fashion doll created by Mattel.
what are they used  for?
They are toys or collectibles. They've been a critical part of the toy market for over 50 years.
where can i buy them ,i think my kids would love it?
doll and her lifestyle.
Mattel has sold over a billion Barbie dolls, making it the company's largest and most profitable line. However, sales have declined sharply since 2014. The doll transformed the toy business in affluent communities worldwide by becoming a vehicle for the sale of related merchandise (accessories, clothes, friends of Barbie, etc.). She had a significant impact on social values by conveying characteristics of female independence, and with her multitude of accessories, an idealized upscale life-style that can be shared
Fashion doll
Fashion dolls are dolls primarily designed to be dressed to reflect fashion trends. They are manufactured both as toys for children to play with and as collectibles for adult collectors. The dolls are usually modeled after teen girls or adult women, though child, male, and even some non-human variants exist. Contemporary fashion dolls are typically made of vinyl or another plastic. Recently, 3D software versions have appeared. 
Barbie was released by the American toy-company Mattel in 1959, and was followed by many