The difference between id, href, uri and external_urls, external_ids
href :: the specific API call to that element. Can usually be constrcuted from uri
uri  :: a unique address to the element. Can be entered in search box. id and type can be extracted from uri
id   :: the 62-bit code at the end of the URI.  *NOT* guaranteed to be unique on its own, without type. Can *not* be entered into search box
external_urls :: a URL that can be put into a web browser. Genereally starts with https://open.spotify.com/<type>/<id>
external_ids  :: a list of IDs used in other systems. Generally consists of ISRC for track and UPC for album 


The results will usually cap at 100 items. 
There will be an element named `next` which will have a URL with the next page worth of data
That page will normally be of the same type as the items