Whether it’s embroidered roses, as seen in the picture above, or lovely white lace sewn on, it is classified as appliqué.
The atelier is where the magic happens- from brainstorming to sketching to creating. This the birthplace of most of the creations that are eventually shown on the runways and maybe even become historically iconic.
Avant-garde describes the designs that make the biggest impressions. People generally view these intricate creations as either genius or design gone wrong. 
When fabric is cut diagonally, or along the bias, hence bias cut- it creates a form fitting shape. This dress shape originated in the 90s, commonly seen on the red carpet. 
In a capsule collection, designers create a few staple pieces that can be mixed and matched to cater to everyone’s personal wardrobe.
These are the clothes worn at red carpets, showcased on runways, and often exclusive to VIPs. All of the designer houses- Chanel, Dior, Gucci, Valentino, etc. create a couture collection for each season.
Je ne sais quoi is often used in fashion to refer to an indescribable appeal. Think The Mega Babe. 
This fancy French phrase- prê-à-porter defines your everyday wear. All designer houses have a ready-to-wear collection in addition to their haute couture collection for each season, but many designers simply only design ready-to-wear collections, for example, Rag and Bone or Elizabeth and James.
Sartorial is more often associated with menswear, but it’s basically a fancy word for clothes/clothes related- ex. Her sartorial choices are very individualistic.