A block is a piece of content that can be inserted into a column instead of using the WYSIWYG text editor. A hide/show or accordion block allows for certain parts of your content to be hidden until the visitor accesses it through a click or tap.
Accordion style content should only be used if the content presented on the page is excessive and may overwhelm the visitor. Many editors use these types of blocks for FAQ content.
Options allow you to have more than one topic or "section" by clicking the green plus to add additional sections.
Visit /it-services-and-support/security/lea-2-step/faq.html for a real time example.
Inside of each section you have "hidden" and "visible" content.