Coconut milk isn't the liquid from inside the nut, but the extract of freshly grated coconut flesh. The flesh is first soaked in hot water, then allowed to cool, after which the liquid is strained off. It's available in tins from Asian and Caribbean stores and larger supermarkets. Coconut cream is sold in hard blocks. It can be diluted with hot water before using or added straight to the simmering liquid in the pan. Both give a distinctive taste and smoothness to curries, sauces and rice.