Finished seams might seem odd for some. Most seams in apparel are serged because most mass retail apparel is constructed using a serger, which automatically finishes and trims the seam allowance. If you ever tried to sew a garment yourself or even tried to take in a garment yourself, you will notice that your seams have what are known as raw edges or unfinished edges.
These edges, if left alone, will fray or unravel until they get down that stitched seam then they will begin to fray into the body of the garment. The way to prevent this is to finish the seam. What this means is that the seam allowance or seam raw edges are stitched in a way to prevent the edges from fraying.
There are a variety of seam finishing techniques. Here is a quick list of some you can look up to find out how to execute the techniques:
Biased-Bound - This seam finish uses bias tape to encase the raw edges. It requires more stitch time than most of the other seam finishes but it results in a more secured raw edge. If planned right can give the inside of a garment a more interesting look.
Hong Kong Finish - This is pretty much the same as the biased-bound finish. However, the Hong Kong finish uses strips of bias cut fabric instead of bias cut tape you buy at the store.
Pinked and Stitched - Basically you sew a straight stitch about 1/4" from each raw edge. Then you trim that edge using pinking shears. This is useful for tightly woven fabrics, especially those that will be lined.
Turned and Stitched - Turn under 1/8" to 1/4"of the raw edge, press it. Then sew a straight stitch close to the folded edge.
Zigzagged - Sew a zigzag stitch 1/4' from the raw edge. Again not one of the most secure seam finishes but it works well on tighter weaves that are light- to medium-weight.
There are other seam finishes you can use. This list gives a mix of some of easy with the more complicated, but sturdier finishes. Of course if you have a serger, you can always serge your seam allowances and call it a day.
Main Image Credit: By PKM (Own work) [Public domain], via Wikimedia Commons