Knots should not be used in an embroidery project unless they are part of the design. Here are the two basic, temporary knots used in embroidery.
An away knot is a temporary knot used to start an embroidery thread. It can be easier to use in embroidery than a waste knot, because you don't have to stitch over the starting end of the embroidery thread to secure it while you stitch. Instead, the starting end of the thread is left in the work away from the stitching (hence it's off name).
An waste knot - like its cousin, an away knot - is a temporary knot used to start an embroidery thread. The thread is secured by stitching over a tail of thread, and the knot is clipped from the fabric after the stitching has been completed.