Parentheses ( ) are a list in Clojure. A left parenthesis is the start of the list and needs a matching right parenthesis or you will get an error.

It is quite common in Clojure code to have many nested parentheses

(def username "john")

(str "Welcome to our website: " (clojure.string/capitalize username))

Next to the parentheses, we see the instructions to the computer. That instruction is normally what we call a function.

The functions do all the hard work in Clojure.

print-str, + and forward are all functions.

When these functions get run, they return a some type of value.

Clojure functions always return a value.

Many functions take in arguments which are everything else inside the enclosing parentheses after the function.

print-str takes "Hello, World!" and returns a string.

+ takes 3 and 4, adds them, and returns 7.

The map function takes the inc function and a collection [1 2 3 4 5] as arguments. map takes a value in turn from the collection and applies the inc function on it, returning the result when all values have been processed.