I don't know the difference between storage for site collection and storage of site.
Can anyone please explain the difference between site collection storage and site storage?
A Site Collection is a container of Sites. (The distinction is clearer for developers as the code objects are named SPSite (for a Site Collection) and SPWeb (for a Site).
A Site Collection has a top level Site. (Developers can create an empty Site Collection, but they are kind of useless.)
Site Collections have Administrators, Sites have Owners. There are Features that can only be enabled for the either Site Collection or only for a single Site.
Site Collections do not have their own lists, libraries or files.
And as a footnote... All SharePoint content by default is stored in SQL databases and tables. Web Applications are stored in databases, Site Collections are stored in Web Applications, Sites are stored in Site Collections and lists and libraries are stored in Sites. I.e. All Sites in a Site Collection must be stored in the same database and that is why we are often focused on Site Collection sizes and limits.
Basically a site collection has a content database in the SQL .
Site collection can store multiple sites and all the data within all these sites lie within the content database . You have control over it .
Site storage is something that is related to content within a particular site .
Since you can make lots of site in a single site collection ,Microsoft didn't give the option to manage this since it will only add to complexity
Long story short , Site collection can be managed by having control over the content database and site storage cannot be managed . That's the only difference.
Mike's answer almost tells everything about it and i will add a bit more facts. The storage limit applies to the site collection as a whole. The files in recycle bin will also count. In other words, the storage limit applies to the total size of the content for the top-level site and for all sub-sites within the site collection. If versioning is enabled, the versions in a site and the content in the Recycle Bins count toward storage limits.
Blogs about sites and site collections:https://sharepointmaven.com/sites-vs-site-collections-in-sharepoint/