While lemon juice and lemon extract are both essentially made from lemons, the difference lies in the parts of the lemon each utilises. Lemon juice is made from the juice of the fruit. Lemon extract is made with lemon peel, or zest, and vodka.
Lemon extract has a stronger lemon flavour and is used in baking recipes to give the essence of lemon without adding acid to the recipe.
Since lemon extract is made from lemon zest and alcohol, the best substitute for extract is the zest or a lemony liquer.
A room temperature lemon poked with a fork or a knife at one end is easier to juice than cutting a lemon in half. It also helps keep the seeds from getting in the way.
Lemon juice has other benefits than in cooking. Lemon juice can be used in cleaning, laundry and hair lightening.
You can buy fresh lemons to make lemon juice or you can buy lemon juice already bottled at the grocery store in the fruit aisle. Lemon extract is usually found on the baking aisle of any grocery store.