There are lots of types of braces.
The most common are fixed braces often called ‘train tracks’.
The basic metal type have elastics (often coloured) to tie a wire in.
There are now more efficient self lifting brackets which use internal springs to hold the wire.
Ceramic brackets are tooth coloured. Whilst not invisible are much less noticeable.
There are many types e.g. twin block. They all act orthopaedically by stimulating changes to ‘bring’ the lower jaw forward.
These are usually made of acrylic and can be taken in and out. They are often useful for minor changes.