Unfortunately not an easy solution. Everyone seems to get trigger points but we don't fully understand the causes. Pain's pretty complex, so some things might work in some cases but not others.

A shortlist of stuff that could help includes exercise, massage (self-massage too), stretching, heat, dry needling or acupuncture. A portion of how much a particular therapy might help can be attributed to your interaction with the practitioner and your personal beliefs around that therapy (see biopsychosocial model of pain). Stress relief, adequate sleep, and improving general health (physical and psychological) can also contribute.

They are formally referred to as myofascial trigger points. The scientific evidence surrounding them is messy and controversial. It's generally accepted that a trigger point is simply a small area of contracted muscle, like a small cramp or spasm. There's also an hypothesis that sometimes a knot/trigger point might not feel hard or tight to the touch when palpating, and is instead a phenomenon related to sensory disturbance.

So to answer the question, it would probably just look like regular muscle, perhaps contracted.