Like ë, ö, etc.
In Latin family languages, French mostly, these are called “diaeresis” markers and mean you pronounce the letters separately. So a fancy way to spell “co-operation” is “coöperation”. Great for names like Zoë.
In German family names, including Swedish, these are called “umlaut” which means “add an e-sound”. Sometimes they sound more like an e than the letter under the dots. Some other languages in the same use a slash through the letter instead, and some paste the actual e on there. ö = ø = œ. Prounced kind of like… “err…” like in bird and nerd and word. ä = æ. Pronounced like air and fair and chair.
Also hëävÿ mëtäl can use them. I mean, use them späringly and respönsibly.
In Scandinavian languages, like Swedish, this is called an “overring” and is used in the letter å and you can think of it as a tiny little o that for some historic and long-forgotten reason have an “a” sitting under it. An “å” walks into the doctor’s office. “Now what in the proverbial is going on here?” the doctor asked the a. But it was the “o” that replied: well… it started at just a li’l zit on my toes… Sounds sorta similar to “saw” or “normal” or the French letter combination “eau”.
In Japanese the ring is called 半濁点 (or “handakuten” which… completely coincidentally is a homonym for the Swedish word for “the hand emergency clinic”) and it means that the syllable is pronounced with a p sound. Easy to remember just thinking of a round pop guard for a microphone, or a round popping bubble.
I’m talking about the ç! “Cedilla” Is what they call that. It started in Spain but they stopped using it but French still does, as a “sibilant marker”. You know how C can sometimes be pronounced like an s and sometimes like a k? The ç is there to make it be pronounced like an s in a particular word, even though other features of the word might lead you to think k. Like, garçon isn’t “garkon”.
In some languages they instead add shush sound. So “ç” is a “church”-like sound in for example Albanian, and “ş” is a is a “shush” like sound in for example Kurdish.
Not the same thing anymore! They, uh, changed it. Latvian has that for some consonant where you use the harder part of the palate to say them. The normal k is like the American word “cut” while the ķ is like the word “key”. A little bit of a “harder” k sound.