where does type detected?

[hibiarata]

I'm newbie of javascript.

Please tell me how detect type in this code.

I understand apiUrl & httpClient is arguments.
export default (apiUrl, httpClient = jsonApiHttpClient) => {

I can't understand this phrase.
return (type, resource, params) => {

Who detect type, resource, params?

I feel that this post is not suitable on this place.Sorry..