A cravat is worn inside a shirt collar.
At the turn of the century the two most prominent styles worn with the popular wing collar shirt were the sailor's knot Teck and Joinville ready-tied neckwear.
The top part of a shirt is called the collar. It is the part that goes around the neck area.
Your shirt collar and your neck
A polo shirt is T-shaped shirt with a collar, typically a two- or three-button placket, and an optional pocket. Without collar, a shirt can not be called polo shirt.
Contrast-Collar Dress Shirts
The button on the back collar of a shirt is called a collar button. It helps the collar keep its shape and stay in place, giving the shirt a more polished look. It can also provide extra support for ties or bowties.
Typically, an ascot is worn around the neck.
The button is designed to keep the collar from rolling upwards and exposing the inside of the collar band underneath. This is specially important if the collar is a soft non fused collar that can roll easily.
it depends on the kind of sportsjacket and shirt you have
The collar position options for this shirt are buttoned-up or unbuttoned.
A shirt collar can be ironed by laying the collar as flat as possible. Using the tip of the iron is best to get into corners easily.
That is commonly referred to as a Henley shirt. It is characterized by its collarless design and partial button-down front.