What the dickens is Bokeh? It is the ability of a lens to be out of focus in a good way. Imagine you are taking a portrait. The person is in front of an expensive, blotchy, painted canvas backdrop, with the paint smeared, streaked, and dripped on to look like nothing in particular, but a nothing that compliments skin tone when it is out of focus. The lens with good bokeh will blur that background in a way that is pleasing. There will be an overall softness to the out of focus background. If the lens has poor bokeh, it will have regular hexagons or circles in a distracting pattern of out of focus shapes.
Most mid-range lenses like the ones that I own have poor bokeh. If I get to a point where I care about what my out of focus areas look like, I'm not going to dash out and get new lenses. I'll fix it in Photoshop.