Sown Tracks are when wefts of extension hair are sewn into tracks created by cornrows, braids or stitched onto the head in either horizontal lines or circles. The extension hair is sewn into the knotted track with a needle and weaving cord.
These extensions can last from 4-8 weeks and can be washed and styled like your own natural hair. Wefts are reusable and can be reused for up to 3-4 months depending on the quality of hair. This hair extensions method is one of the oldest ways to achieve length and fullness.
The only drawback is that it can cause traction alopecia and tends to cause a very sore scalp for up to a week or two depending on your sensitivity. If done too tight it can pull your own hair out of the head. I do not recommend this method for anyone with fine or thinning hair.
Glued Tracks wefts are available with all types of human and synthetic hair. The higher the quality of human hair the more expensive it will be per weft.
A bonding glue or adhesive material is brushed onto the weft of the extension hair and then it is applied to the root of your own hair. The extensions can be easily removed by a bonding remover. There are many types and variations of adhesives available, including waxes and medical grade adhesives. Please not that there have been cases where women had an allergic reaction to the bonding material, so I always recommend to do a patch test on your arm.
This method is for temporary extensions when you want you want to add some length or volume. It will last up to a week or until the first time you shampoo your hair. Unlike sown tracks, with glued tracks there is no need to create tracks of your own hair prior to installing the extensions. They do last a bit longer than clip ins especially for women who have really short hair and purchase really long clip ins.
Glued tracks have to be purchased or cut to the prefect layered lengths to blend well and look real. They lack natural movement and can look bulky on the head if too many are applied in attempt to create volume. Hair can be reused depending on the hair quality and glue/bonding agent.
For further reading you can check out the methods comparison table.