Chard is very closely related to beet, and indeed they are the same species. The only difference is that chard is bred for the leaves and stems, beet for the root.
Chard can be used just like spinach, and you can eat the stems as well as the leaves. You take a few of the outer leaves at a time, and the plant will keep producing over a long period, perhaps more than a year if conditions are good. I usually wash the leaves and stems, chop, and then put them in a pan with a little butter over a moderate heat, stirring them around occasionally. The water content comes out in the pan, and the volume reduces quite a lot, and when they are nicely softened a little sour cream goes nicely with them.
FWIW you can do beet tops exactly the same way.
