What is shortening?

Biscuits are made with “shortening “. The fat is rubbed into the flour and molecules of fat surround the flour particles and prevent water mixing with flour, which stops the development of gluten in the dough. The fat is said to shorten the dough. Shortening promotes tenderness in the biscuit and prevents excessive gluten development during mixing. Without shortening, biscuit dough would be tough and rubbery, which would result in biscuits being dry and lacking in the desired eating qualities. Shortening contributes to the spread of the biscuits. Hydrogenated shortening with a bland flavour which is commonly used, although butter produces biscuits with a more desirable taste and flavour
NB: In this answer 'biscuit' can be interchanged with the term 'cookie'.