Type-aliases explanation

book/src/language-tour/type-aliases.md

@@ -1 +1,24 @@
 # Type aliases
+
+A type alias lets you create a name which is identical to another type, without any additional information.
+We like type names (including type alias names) to be PascalCase.
+
+```gleam
+type MyNumber = Integer
+```
+
+I imagine them like variables for types. You could use this to simplify your type signatures for tuples.
+
+```gleam
+type Person = (String, Integer)
+
+fn createPerson(name: String, age: Integer) -> Person {
+    (name, age)
+}
+```
+
+If you want the type-alias to be accessible as a module, you should pub it.
+
+```
+pub type MyVector3 = (Integer, Integer, Integer)
+```