A buckle is a type of fastening usually used on leather belts and shoes. Buckles can be adjusted, as the prong part of the buckle fits through a hole, and you can have many holes on a strap.
A button is a small, usually flat object that you use to keep your clothes shut. Buttons can be made of wood, metal shell or plastic. There is usually some holes through the button or a loop under the button so they can be stitched to your clothes. You fasten a button by passing it through a matching hole.
Crochet is a way of making cloth out of loops of yarn using a small hook. Crochet is different to knitting as there is only ever one loop at a time, while knitting has many loops along the knitting needle.
Embroidery is a way of placing stitches so they make patterns or pictures. The most common thing people embroider is flowers. Embroidery is often seen on clothes to make them look prettier, or as samplers to hang on the wall.
Fabric frays when it starts to come undone, and starts to turn back into the individual strands it was made from. A fray is also a battle or fight, and is often used as a turn of phrase when you are about to go into the middle of some activity, eg "he stepped into the fray".
Fabric is gathered together by stitching it in such a way that it bunches together, like you see in the picture. Skirts are often gathered onto a waistband. Gathering also means collecting things together - see gather.
A hem is the stitching along the edge of a garment. Hems make the edges of clothes look nicer, and stop them from fraying.
Knitting is a way to turn thread or yarn into cloth. Knitting consists of loops called stitches pulled through each other. The active stitches are held on a knitting needle until another loop can be passed through them.