This should perhaps have been the first post in this series, but it was only when I was talking to someone this morning that I was reminded what exactly vermouth is, isn't exactly common knowledge.
The short answer is that it's a fortified wine flavoured with various botanicals, herbs, and spices. The long answer is a bit more complicated. It takes in a whole host of styles, as well as closely associated drinks - Americanos, Chinatos, Barolo Chinato, and Amaro's. Americano, like Amaro are bitter drinks (think Campari or Aperol). Chinato is more like vermouth, and maybe easiest to think of as having a more medicinal history, they have chinchona (quinine) as a major flavouring, so again more bitter than vermouth tends to be.
It's easy to get confused amongst all this, even more so because only a very few of the very many styles are likely to be easily available to us on the high street. My local M&S sells one Vermouth, Tesco has an own label range that I don't find inspiring, Waitrose has a better selection, which if limited if you want to seriously explore, does at least have a lot of things I like, my local wine shop is equally limited, though again with a couple of good things in it.
Serious exploration calls for a more expert guide (I'm recommending 'A Spirited Guide to Vermouth' again, which lists a whole range of products) a good book on the subject is definitely helpful. It will definitely help with drawing up a wish list of styles or specific products, which will then call for a whole lot of research regarding where they can be bought (and possibly if they're worth investing in).
The origins of vermouth as we know it now are mid 18th century, but the history of fortifying and flavouring wine goes back a great deal further. Coming at it from a British perspective, and as a woman of a certain age though Vermouth has a specific set of associations. I'm old enough to remember the Martini adds of the late 1970's/early 1980's which gave it a sort of continental glamour, but with a distinctly tacky edge. Competing with that is an altogether more sophisticated image of pre war glamour fuelled in equal parts by P G Wodehouse and the Savoy Cocktail Book.
I'm interested in the current renaissance in Vermouth making (I'd particularly like to try some of the things Sacred are doing) but they are comparatively expensive, and they don't have quite the same romantic appeal to me that some of the old brands have.
It doesn't take long with something like The Savoy Cocktail Book to realise what a big deal Vermouth was in the 1920's/30's cocktail world, and only one Martini where the proportions are 1 part dry French Vermouth to 2 parts gin to give that flavour a particular association. I like the older brands of vermouth for the same sort of reasons I like classic scents from old perfume houses.
Chanel N°5 might have been through various updates and reformulations but at its heart there's still all those decades of glamour, it and its sisters of a similar vintage have a complexity that's very distinctive. Vermouth does the same for me in terms of flavour.