They're not the same
Sure, we all basically know what porridge looks like, but what is porridge, exactly? And what is the difference between porridge and oatmeal? (And while we're at it, what's the difference between porridge and grits and gruel? I mean, I've seen Oliver! and the stuff in that cauldron looks like porridge to me.) Turns out it's totally OK if you've lived your whole life calling a bowl of oatmeal "porridge" because oatmeal is, in fact, a type of porridge. But in the same way that not all rectangles are squares and not all pop stars are Beyoncé, not all porridges are bowls of oatmeal.
Porridge is basically any grain—be it oats, corn, even rice—that is cooked and boiled in water or milk until it has that creamy, thick consistency that we all know as, well, porridge. It's also sometimes called "hot cereal." You know what it looks like when you see it: a gloppy bowl of something distinctly cream-colored.
You can enjoy your porridge on the chunkier side, such that you can see individual oats in the bowl; that's generally considered to be oatmeal. But in the most traditional British sense, creamy porridge is made with oats that have been cooked down until the actual oats have kind of melted, and you can't really tell where one oat flake ends and one begins. As British chef Jamie Oliver explained on his website, one "vital tip" when it comes to making perfect porridge is that "you need those oats to break down, and the best way to do that is stir until your arm seizes up." (Sexy, I know.) And to get that texture and prevent clumps of oats, there's even a specific spoon that you can use to get that arm workout, called a spurtle.
Porridge isn't limited to oats, though, and the idea of boiling grains in milk or water until it's thickened isn't unique to British cuisine. There are versions of porridge around the world that make the most of whatever grains might be commonly available in those different countries. Throughout Asia, for example, there are several different variations of rice porridge, broadly called congee. These dishes are generally savory, made with rice and water or some kind of animal broth.
Really, the possibilities are endless, and you can find example of porridge from different cuisines around the world. Porridge made from sorghum is found in South Africa and Papua New Guinea. Ruispuuro is a type of Finnish porridge made with rye and water. Buckwheat porridge, also known as kasha, is commonly eaten in Russia and eastern Europe. Genfo is an east African porridge made with barley flour. Then there's upma, a savory porridge from southern India made with semolina. Even grits, in the most technical sense, are a type of porridge, made from corn.
There are so many different textures, ingredients, and toppings that can be considered part of this relatively simple dish, so it's totally possible to be a staunch oatmeal hater and still find a porridge you love. You just have to give porridge a chance.