It is an array with fixed length and fixed value. Example:
const role = [4, "teacher"];
Above array elements have a meaning.
4 is role id and
"teacher" is role description. Any other array values like,
[4, "teacher", true] is invalid.
Here is how we can set a tuple type using TypeScript.
let role: [number, string];
Above type says,
role can have an array whose length should be 2. Also, the first element should be a number and second one a string.