Erbette is part of the leaf beet family, like chard and perpetual spinach. I think it comes from Italy
Anyway, it is as said previously, much milder than both the others in taste, the leaves are more tender and the stems are thin. You can pick young leaves for salad or use full sized leaves as spinach. The leaves are large, so its quick and easy to pick as well. Like chard and perpetual spinach, pick what you need and leave the plant to make more.
I chop it up and add into sauces, curries and soups at the end of cooking just to wilt it. If I just want wilted greens to eat, I put leaves in a colander in the sink, pour a kettle of boiling water over it, leave it for a few minutes, then press the excess water out.
Chard and perpetual spinach need a bit more cooking. I usually blanch in a pan of boiling water by putting them in stems first and feeding the leaves in as the stems soften. You can switch the heat off at this point and leave them to sit for a minute or two, then drain, squeeze out excess water once cool enough to handle and chop. You can also split leaves and stems as use in different dishes like DHM says.
Once you start cooking such veg, a massive pile wilts to not much at all, so its easy to keep picking and then the leaves stay fresh tasting and fairly tender. I think most people who say they don't like chard or perpetual spinach leave it to grow too long before picking. Older leaves are a bit tough and have a more pronounced taste.
I grow all of them and more types on top, as we eat loads. Leafy greens are so tasty, easy to grow, easy to incorporate into meals and are full of good stuff. I'd say get growing and get 'em down you