Gather (sewing) explained
Gathering is a sewing technique for shortening the length of a strip of fabric so that the longer piece can be attached to a shorter piece. It is commonly used in clothing to manage fullness, as when a full sleeve is attached to the armscye or cuff of a shirt, or when a skirt is attached to a bodice.
In simple gathering, parallel rows of running stitches are sewn along one edge of the fabric to be gathered. The stitching threads are then pulled or "drawn up" so that the fabric forms small folds along the threads. 
- Pleating or plaiting is a type of gathering in which the folds are usually larger, made by hand and pinned in place, rather than drawn up on threads, but very small pleats are often identical to evenly-spaced gathers. Pleating is mainly used to make skirts, but can have other uses.(See main article Pleat.)
- Shirring or gauging is a decorative technique in which a panel of fabric is gathered with many rows of stitching across its entire length and then attached to a foundation or lining to hold the gathers in place. It is very commonly used to make larger pieces of clothing with some shape to them.
- Caulfield, S.F.A. and B.C. Saward, The Dictionary of Needlework, 1885, facsimile edition, Blaketon Hall, 1989, p. 219
- Picken, Mary Brooks: The Fashion Dictionary, Funk and Wagnalls, 1957. (1973 edition ISBN 0308100522)
- Caulfield and Saward, The Dictionary of Needlework
- Caulfield and Saward, The Dictionary of Needlework, p. 220