
Vanilla extract is an alcoholic flavoring made by steeping cured vanilla beans in a mix of alcohol and water, drawing out their aroma.
Half a split vanilla pod steeped in the spirit for a day gives a rounder version and costs a fraction. Vanilla syrup carries the aroma with sugar attached, so a barspoon of it replaces two drops of extract and roughly four grams of sugar has to come out elsewhere. Vanilla paste is extract with the seeds left in and doses the same. In an alcohol-free drink, remember the extract carries alcohol and the syrup does not.
Vanilla essence
A synthetic-vanillin imitation that need not contain vanilla at all and is often alcohol-free. Use rather less of it and expect one note instead of a chord.
Vanilla syrup
Sugar-led, so it sweetens as it flavors. Swapping extract for syrup drop for drop does nothing; swapping by aroma means taking sugar out of the recipe.
Sealed and dark it keeps for years, because the alcohol preserves it: an old bottle is weaker, not spoiled. Imitation essence fades faster and can pick up a flat, cardboard note. Store it away from the heat of the machine, since the aroma leaves through a badly closed cap.