It’s the first thing we all learned how to make with crochet. From the chain we build the garment we plan to make.
Does it matter if the chains are all the same size? Yes! Not only that, if you plan to do a row of sc onto the chain, the chain loops need to be similar in size to your sc. In other words, if your loops are loose and your sc is not then you will have a sloppy looking edge on your garment.