Artificial Languagesaka: Planned Languages, Constructed Languages (Conlangs), Auxiliary Languages (Auxlangs)
They're actual languages, possessing vocabulary and grammar, but they were contrived by eggheads. Some of them require custom alphabets. There are thousands of such languages; here are just a few of the most famous.
The early history of artificial language is intertwined with the occult, and the desire for a real character (in other words, the One True Word that all humans, no matter their original tongue, would understand.)