What is meant by elasticity of demand and inelasticity of demand?

Question

Price. Can anyone give me some examples to aid in the understanding?

Answer 1

Elastic demand:  The generic groceries at the store.  If price goes up a little, everyone will just switch to the generic brand at another store.  (People buy less if price goes up)

Inelastic demand:  Oil.  Everyone thinks they gotta have it, any price.  (People keep buying, even when price goes way up)

Answer 2

inelasticity demand would include water and air. Not that we necessarily "buy" it on the open market, - but we need what we need.

elasticity would include DVD / movies. Dropping prices (or raising prices) by 1/3 may cause sales to increase / decrease by 100%

Just a guess, if increasing gasoline prices by 10% does NOT reduce demand by the 10%, then that's IN-elastic.