I need to understand this part of the code

let x = "hello my name is chrono"

const finalSentence = x.replace(/\S\w | \s\w/g, letter => letter.toUpperCase());

>>>>>>>>>>>>> I need to understand this part of the code >>>>>>>>>>>> letter => letter.toUpperCase()

Is it like writing this

function letter(letter) {
letter.toUpperCase()
return letter
}