Dresses during the regency period were exceedingly thin and simple. After the gigantic-dress of the Elizabethan period, this was a huge change. No more dense layers of fabric, no more pounds and pounds of weight on you. This was very freeing and wonderful - but it also could be rather chilly in drafty English homes!
Regency Period and Jane Austen
Enter the fichu. The fichu was a gathering of lace added into the bodice so that the same dress could be worn both on hot days and on cool, on daily occasions and for more formal fancy wear.
In essence, you could make a dress with a very open bodice, for formal wear. But then for daily wear around the house you could put lace into that bodice area to stay more warm and to not be as exposed. Many dresses also had long sleeves you could put onto them, to keep your arms warm.
Below, Elizabeth Bennet from Pride & Prejudice BBC wears a lace fichu in the center of her yellow dress.
Here's Elizabeth in the same series with a very subtle fichu, more for show than anything else.
A much more full fichu. You can see how removing it would make the dress quite pretty.
Sister Mary wears a more elaborate fichu.
Regency Period Information