Heading tags

Header (or Heading) Tags (HTML heading,HTML Header tags) and subheading tags are critical components of search engine marketing. Optimally, page titles should also be included to clearly define the page’s purpose and theme. All of the header tags should be used according to their relevance. The most important tag is the <h1> heading tag, and will usually be the title of a page/post. Heading tags have hierarchy from <h1> to <h6>.
Header Tags are used to differentiate the headings and sub-headings of a page from the rest of the content. , and It has an impact on both the SEO and usability of your site. There are things you shouldn’t be doing with heading tags: Do not stuff them with keywords, not more than one h1 tag on a page, no heading tags in hidden text, different heading tags on different pages etc.

Additional Terms:

Rich Snippets
Ecommerce
Social Media
Yandex
Search Engine Reputation Management (SERM)/ Online reputation management (ORM)
Google Partner/Premier Google Partner
Responsive Website
Mobile-Friendly website
Google maps
Hashtag
Call To Action
Bounce Rate/Abandonment Rate
Mobile Marketing
Content Marketing 
Marketing Automation / Programmatic
Website Traffic/ Traffic Analysis
Geo Targeting
Quality Score
Lead Generation
A/B Testing
B2C Digital Marketing
B2B Digital Marketing
Doorway page
Dead/ Broken link
Wikipedia
Robots.txt
Internal Link
Outbound Link
Inbound Link
Google Trends
Google Sitelinks
Google Keyword Planner
CTR (click-through rate)
CPC (Cost Paid per Click)
404 Not Found
Redirect 302
Redirect 301
200 OK Code
Alt attribute/ Alt tags
Nofollow link
Search engine algorithm
White hat search engine optimisation
Black hat search engine optimisation
White hat SEO
Google’s Penguin Update
WordPress
Usability
Organic Search Results
Link Building
Landing Page
Google Dance
Indexing
Email Lists
Duplicate Content
Domain
Canonical URL
Blog
Banners
Algorithm
Accessibility
Conversion Rate
Satellite Websites
Bid
Joomla
Google’s Knowledge Graph
Drupal
Link Exchange
Long tail
Google Webmaster Tools
Lead
Magento
Keywords
Mini Site
Search Engine
CMS
Site Map
Player Embed
Bread Crumbs
Google Panda Update
YouTube Channel
Contextual Advertising
Open Source
Google’s Search Engine Robot
Meta Tags
Affiliate Program
CPA - Cost Per Action
CPL - Cost Per Lead
Friendly URL
GDN – Google Display Network
Page Rank
Remarketing
ROI – Return on Investment
RSS (Really Simple Syndication)
SEM-Search Engine Marketing
XML–Extensible Markup Language