Zig zag seam
Zig zag is the most predominantly used seam pattern in lingerie. This seam is formed in V shape when it runs through the fabric forms a zig zag pattern. Whether be it encasing the elastic or to attach any delicate lace to the fabric it prevents the raw edges from raveling off while giving room for stretch without breaking. Foam pads in a padded bra are stitched with zig zag seam. it is used to attach embroidery appliqué to sheer lingerie. Also you would have noticed some panties have zig zag seams on elasticated waist band and leg openings.
3 point zig zag
This is just like a zig zag seam but there are 3 stitches in the place of a single stitch. It has the same purpose as a zig zag but provides better reinforcement where ever needed especially, bra band, arm hole, panty waist band.
Over lock seam
Usually done by a serger machine for lingerie finishing. It cuts the extra seam allowance covering the raw edges with interlacing stitches simulatneously.
This resembles an over lock seam on the inside and a 2/3 sets of plain stitches on the outside of the fabric Most commonly used on the elasticated lingerie hemlines.
This is just another form of over lock seam. As the name suggests the stitches are smaller compared to an over lock seam. It is used for hemming light weight and delicate transparent lingerie.
A bartack sewing machine is used for stitching. A bartack seam is very intricate and very time consuming, hence expensive. It is used to seal under wire casings, and rigid frame like structures like corsets. A bartack seam is also used to fix raw elastic edges. The pattern is similar to zig zag but very closely stitched and very difficult to unravel the seam. Expensive luxury lingerie has bartack seams. A bartack seam is used at the bra apex to join the strap with the cups to give maximum reinforcement.
French seam is used to enclose the raw edges and gives a neat look. A narrow seam is considered the best. It is used only on non-stretchable fabric. The seam is perfect for finishing the raw edges of light weight and transparent fabric. It gives a neat and clean look and protect the fabric from fraying away.