Egg production involves the use of (and often the abuse of) chickens.
Most eggs are still produced using battery farming techniques, which involve cooping chickens in extremely confined cages, often so that they have no freedom of movement at all.
'free range' eggs, are more expensive but are layed by happy chickens which are free to roam around, and have access to an outdoor environment. There are strict rules about what constitutes 'free range'.
'barn' eggs are a mid-range comprimise. These eggs are laid by chickens which are kept in a barn, but are not kept in cruel batteries.
Chicken meat producution can also involve cruel caging of chickens.