I think it comes from the higher shoulder area of the cow braising steak usually has a bit of fat with it .

Another cut that braises well although does not have much fat and has long thicker fibers to the meat is flank .
This I think comes from the lower side of the cow toward the back of the cow . ( almost underneath ) .
My family love braised flank steak . I think they prefer the taste to braising steak .

(I don't eat meat myself but cook it for my family .)

hippytea wrote:

Or brisket - from the dangly bit between the front legs.

The FRONT legs. Don't be confused.

   

It may be difficult to order cuts from between the front legs by pointing to my own body!

But cheers, I'll give the belly area a go.

You could print out a picture of a cow, or even one of those diagrams with the different cuts on it, and point. Of course, that depends on whoever is selling you the meat having some butchery knowledge!

The cut you bought would have been better for roasting.
I bought quite a large amount of flank beef yesterday , its a pretty lean flavourful cut . We had visitrs for supper and I put it in the slow cooker with
a chopped onion,
a few chopped sticks of celery ,
some herbs and a couple of bayleaves,
2 tins of tomatoes and some tomato pure,
salt and pepper  seasoning ,
spoonful of mustard and
a spoonful of redcurrant jelly and a pint of beer.
I slow cooked it all day and shortly before our freinds arrved I took ot a lot of the juices and reduced them in quantity by simmering the pan of juices in a saucepan.
the added the reduced quantity back into the slow cooker .

I am told that is was realy very very nice, but being vegetarian myself I have to rely on what they tell me.The gravy that came from the slow cooker was rich in flavour.
Must have been good as there was a huge bowl of it and they all has seconds !

I tend to avoid too much fat when braising, as it won't all render out and what's left goes rubbery. A bit of thin marbling is good, but anything more and I prefer to trim it.

For fatty cuts, a good hard browning helps it to render, though.