First we will focus on the absolute basics.
BJD stands for “Ball Jointed Doll”.
Although ball jointed dolls can be traced back to multiple points in history, I will be focusing on the modern usage of the term.
A Ball Jointed Doll is typically a Resin doll with ball joints, strung together by elastic. They are highly customisable; Eyes, wigs, clothing etc are interchangeable and many collectors customise the face paint (known as a Face Up) to further personalise the doll to their collection.
BJDs come in various sizes, anywhere from a few inches tall, to a meter high. The most common sizes are categorised by scale or by cm. Here is a quick overview of the terms used to describe these sizes;
1/6 = Under 30cm = yosd
1/4 = 40cm = MSD
1/3 = 60cm = SD
65cm = SD17
70cm = Uncle
Dolls come in a huge variety of heights outside of these measurements and the above is merely an illustration of what is available.
Wikipedia has an article which covers the history of BJDs with more detail; https://en.wikipedia.org/wiki/Ball-jointed_doll .
Please click on the menu drop down for more information about BJDs.