What is a connector?
With one click, a connector creates an item in your Zotero library, with bibliographic information and optionally, when available, a full-text screen capture or PDF.
Zotero connector icons generally appear to the right of the URL bar in Chrome and Firefox.. Here is what some of them look like.
Examples of Zotero connector icons:
Book:
Journal Article:
Magazine Article:
Blog Post:
Video Recording:
Audio Recording:
Newspaper Article:
There are a couple of dozen other icons representing other document types (Conference Paper, Dictionary Entry, Image, etc)
Mac users should consult this page: https://www.zotero.org/support/kb/safari_compatibility
Zotero has been programmed to extract relevant metadata from many sites, both academic and non-academic. But it is not programmed to recognize every site.
For example, on the New York Times site, Zotero will give you a newspaper connector icon 
when you are on the page specific to that article, and when you click on that icon Zotero will correctly get and file all the relevant metadata you need for your citations.
Although the Socialist Worker is also a newspaper site, Zotero has not (yet) been programmed to recognize articles at https://socialistworker.co.uk/ , so you will not see the newspaper connector icon for the articles there. Zotero offers 'generic' icons for web pages that it isn't programmed to recognize. When Zotero doesn't really know what's going on, it will offer one of the following:
This blue generic connector will create an entry for a document type "Web Page" which will include the title of the page, the URL, and a snapshot. This is useful, but you have to type in the rest of the bibliographic information by hand (you will also want to change the Item Type (for example, from Web Page to Newspaper Article), and you will find that the title of the web page captured by Zotero is not always the title of the article on that page).
The gray generic connector usually means that the page has not finished loading, so Zotero hasn't yet had a chance to fully interpret the document. You should not click on the grey icon: wait for a real connector icon to appear when the page has finished loading.
You may sometimes see the Zotero "Z" icon This icon indicates that Zotero is active on your machine -- it is not really a connector.
When you click on a connector, a small popup window will appear, showing that Zotero is in the process of saving your citation (and pdf or snapshot if relevant). Sometimes this box appears and disappears so quickly you may not notice it. That is ok. Once the box is gone, that indicates that the item has been saved. Sometimes the box sticks around for a few seconds. Text in the box indicates what Zotero is saving. The text is grayed out when the saving is not complete. When the text goes solid-black, that means it has been saved to Zotero. Usually the citation saves first, then pdfs or snapshots. Anything that is still grayed out in that box when you leave the web page will not have been saved to Zotero.
If there is an error saving your item, this will be indicated in that box. The two most common errors are failure to save the item at all, or failure to save an pdf or snapshot..
