There may be some confusing acronyms or words, the below is what we mean when we use them.

CMS, a content management system, this is where the content/data is managed. More info

Theme, a set of files that should mostly be used to change the appearance of the content, the theme can also extend the sites functionality but this should be done with a plugin where possible. More info

Child Theme, add additional styling and/or functionality without changing the parent theme. Using a child theme enables the administrator to update the (parent) theme without losing the additional styling provide by the child theme. More info

Plugin, used to provide additional functionality to a WP site. Plugins can often be used on any WP site, an example of a WP plugin is Yoast this plugin provides additional data fields on a page or post that allow the user to add SEO meta data. More info

Category, a hierarchical, parent-child taxonomy.  More info

Tag, a non hierarchical taxonomy. More info

WP Theme and Plugin repo, a place where WP approved themes and plugins are stored and managed. We do not plan to add out themes and plugins here as they require additional work and management, we plan to release our theme to GitHub. More info here and here.

Widget, a small block that performs a specific function. You can add these widgets in sidebars, no longer commonly used. More info

Short Code, some plugins and theme enable the use of short codes to display content in a page. For example you could have a short code like [date] that would display today’s date, this is often used to display plugin functionality in pages or in widgets. More info

Custom Post Type, a way to abstract data in WP, by default WP has Pages and Posts (as well as others like users and media). Themes and plugins often provide additional CPTs, for example you may have a FAQ plugin that provides an FAQ CPT. This will give the user a tab that contains all the FAQs, each FAQ would probably contain the question, answer, author, date etc. More info

Post Meta, additional data save to a post (or page). More Info

Meta box, a UI in the CMS for editing the additional meta data saved to the post (or page) or component/block. More info

Theme Options, this allows the CMS user to save data that can be used across many pages, usually used for data such as social icons, or an address, so the CMS user only needs to update the info in one place.

Component (block), usually a reusable block of HTML that can be added to the front end of the site. When a component is added to the page in the CMS a set of fields are added to the page which are required for the HTML displayed in the front end. A reusable set of fields in the CMS that usually shows in the front end of the website. More info

Blocks, the word used by WP to describe repeatable parts of a webpage. 
More info

Layout/grid, an area that components can be added to in the CMS. For example you may have a single column layout containing components or a layout that has a main content area and a right hand side ‘sidebar’ both containing components.

Guttenberg, the new WordPress editor, design to remove the need for ACF, short-codes and widgets More info

Templates, pages can be assigned a template, a template usualy provides some special functionality to a page or set of pages. For example the search results page may have a special template for displaying the search results and the blog/news page will have a special template that loops through and paginates all of the news content. More info