So there is an item ID, a summary and a description. The item ID determines the URL (and I will never repeat the mistake to make that very long!).
Right so far.
The index will list item ID + description, the comment headers will list summary + description. Apparently summary and description are set to the same text when first submitting a new article? It is the summary that can be controlled by the author through the 'Edit index information', as 'Item name'.
I don't think this is right.
The Summary is also called the Item Name, and the latter name is perhaps clearer. The Description is a one-sentence(ish) blurb. The ItemID is a unique permanent identifier, which the URL is also based on. Then there are Index Entries, with a Link Text and Link Description; these are used on search pages (except What's New, which has its own description), and the header on comment threads use the Item Name and the Link Description (???).
When you first submit a page, you provide an Item Name and a Description. An ItemID is created based on that Item Name (generally with a prefix MS, MP, etc. and with spaces replaced with hyphens, etc.). The ItemID is meant to be a permanent unique id, and the URL for the page is based on this ID as well.
The Description that you provide when you first submit a page just populates the initial Index Entry, together with the Item Name. Most pages will only ever have this one Index Entry, but you can have more; see in particular the Piececlopedia, where a piece with multiple common names is given and Index Entry for each name, for ease of discovery. (We also distinguish "Primary" index entries, and the query can filter down to only those primary entries if you don't want the duplicates.)
You can update the Item Name. This will not update the ItemID nor URL (because those are meant to be permanent), so these can diverge. Also, changing the Item Name doesn't update the Index Entry, which might be a little confusing. I think users can't add index entries (perhaps to prevent exploiting them for greater visibility), but updating them may be made available.
Right so far.
I don't think this is right.
The Summary is also called the Item Name, and the latter name is perhaps clearer. The Description is a one-sentence(ish) blurb. The ItemID is a unique permanent identifier, which the URL is also based on. Then there are Index Entries, with a Link Text and Link Description; these are used on search pages (except What's New, which has its own description), and the header on comment threads use the Item Name and the Link Description (???).
When you first submit a page, you provide an Item Name and a Description. An ItemID is created based on that Item Name (generally with a prefix MS, MP, etc. and with spaces replaced with hyphens, etc.). The ItemID is meant to be a permanent unique id, and the URL for the page is based on this ID as well.
The Description that you provide when you first submit a page just populates the initial Index Entry, together with the Item Name. Most pages will only ever have this one Index Entry, but you can have more; see in particular the Piececlopedia, where a piece with multiple common names is given and Index Entry for each name, for ease of discovery. (We also distinguish "Primary" index entries, and the query can filter down to only those primary entries if you don't want the duplicates.)
You can update the Item Name. This will not update the ItemID nor URL (because those are meant to be permanent), so these can diverge. Also, changing the Item Name doesn't update the Index Entry, which might be a little confusing. I think users can't add index entries (perhaps to prevent exploiting them for greater visibility), but updating them may be made available.