There are generally two that are called extracts. One is an alcohol based product, they steep the vanilla pods/pieces in alcohol to extract the flavour and of course this comes with some colour from the actual vanilla. This is also sometimes mixed with a small amount of sugar. It is an actual vanilla product just diluted. The other one called extract or essence is produced by using glycerine to achieve a similar result but is non-alcoholic. You may also find Vanilla Paste which is a more concentrated form of vanilla, I am not sure how it is produced but I am sure it can be looked up. Once you use the paste most do not go back to the essence/extract, the paste flavour & smell is more vanilla intense.
The imitation vanillas use one of either two man made chemicals one that is named vanillin that is the same major flavour chemical in Vanilla that is 4-hydroxy-3-methoxybenzaldehyde or it’s stronger relative ethylvanillin which is 3-ethoxy-4-hydroxybenzaldehyde. Ethylvanillin is used a lot in Chocolate.
