Many people who start out with embroidery as a hobby will spend a lot of time looking for all the equipment they need. A circle or embroidery frame is actually not an important item of equipment although it will greatly assist you in embroidery.
The embroidery circle is usually made of two separate parts, one loop where you place the fabric, and the second loop that you place on the fabric to hold it. The upper circle is also as a nut, which is tightened to ensure the fabric stays in place. These embroidery circles come in a variety of sizes ranging from small ones to embroidery items intended for use with cards, to very large ones for large embroidery projects such as pillowcases or wall hangings. Today, embroidery is made of various materials, but the most common are plastic and wood. Depending on the type of wood used, prices for these embroidery cords can vary dramatically.
The embroidery cord serves as a tightening of the fabric you want to use, to allow easy embroidery. Often you don't need a big circle to cover the whole project, you can use a small circle and move the circle to the area where you need to use it, because the embroidery knots are very easy to improve. The bad side of most embroidery is that they are not free standing, but you can buy a stand for them from a number of hobby shops, though this might not be ideal. Try to buy a stand by your manufacturer or circle.
This is a hobby that generates economic value for it, be enthusiastic about the hobby that you like.
Hopefully this explanation is useful.