You wouldn't like it. A marmite is a very small casserole dish, marmite, the product is yeast extract.
It's got a salty/beefy taste. People, places, things are often described as being marmite in that you either love it or hate it.
That's what the adverts say, but I don't love it, I quite like it.
The people who like it tend to be the people who were given it when they were being weaned, (lots of B vitamins.)
I doubt very much you were given it as a kid so chances are you won't like it.