Tengwar is the fictional script J.R.R. Tolkien devised for writing languages such as Quenya and Sindarin. The word tengwar means “letters” in Quenya, one of Tolkien’s Elvish languages.
Tengwar is an abugida-like writing system whose signs primarily represent consonants, while vowel marks, called tehtar, can be placed around them. Tolkien designed several modes of the script so that it could represent different languages, including Quenya, Sindarin, and English. The system therefore has a flexible relationship between signs and sounds.
Tengwar is often confused with Cirth, another writing system in Tolkien’s legendarium. Cirth uses angular rune-like characters and was particularly associated with Dwarves, while Tengwar has more flowing forms and is strongly associated with the Elves. Sarati was an earlier script in Tolkien’s invented history of writing, making it a related but different answer.