Yes — identical seed, two names. UK shops tend to say linseed, while "flax" is more common in recipes written for an American audience. If a recipe calls for either, this is the bag you want.

Ground, mostly. The seed has a hard, smooth coat and a good proportion passes through undigested, so you get the fibre but little of what is inside. Grinding a batch in a spice grinder solves it. Whole seeds still work well baked into bread.

Whole seeds keep for months in a cool cupboard. Ground does not — the fats begin to oxidise once the seed is broken open. Grind small amounts, keep them airtight in the fridge, and use within a couple of weeks.

One tablespoon of ground seed stirred into three tablespoons of water, left for ten minutes, thickens into a gel that binds in baking. It works well in pancakes, muffins and cookies. It will not do the lifting an egg does in a sponge.

They are notably high in fibre and are one of the richest plant sources of alpha-linolenic acid, an omega-3 fatty acid. They also carry protein and minerals including magnesium. A tablespoon is a small amount, best treated as an addition to a varied diet.