HTML5 is the fifth revision of the Hypertext Markup Language, which is the standard language used to create and design web pages. Understanding the basics of HTML5 is essential for beginners who aspire to build websites or web applications. At its core, HTML5 provides a structure for content on the web, allowing for elements such as headings, paragraphs, and lists. With the introduction of new semantic elements like <header>, <footer>, and <article>, HTML5 enhances the way content is organized and understood by both browsers and developers.

In addition to semantic tags, HTML5 has introduced various features that improve the functionality of web applications. For instance, the <canvas> element allows for dynamic, scriptable rendering of 2D shapes and bitmap images, making it a popular choice for game and graphics developers. Moreover, HTML5 supports multimedia through native <audio> and <video> elements, which enable developers to embed sound and video content without relying on third-party plugins. By mastering these fundamental aspects, beginners can begin to harness the power of HTML5 to create engaging and interactive web experiences.

HTML5 has revolutionized the web development landscape with its myriad of features that enhance functionality, streamline development, and improve user experience. Here are the top 10 HTML5 features every developer should know:

1. Semantic Elements: HTML5 introduced new semantic elements like <article>, <section>, and <header> which provide meaning to the structure of the web page, helping both browsers and search engines.
2. Canvas: The <canvas> element allows developers to draw graphics and animations on the web in real-time using JavaScript, giving rise to dynamic content that keeps users engaged.
3. Video and Audio Support: With <video> and <audio> tags, HTML5 enables native embedding of rich media without the need for third-party plugins, enhancing accessibility and performance.
4. Geolocation: HTML5 offers a geolocation API that provides accurate geographical information about users, making location-based services easier to implement and improving personalization.
5. Local Storage: The introduction of local storage allows developers to store data within the user's browser, enabling faster access and a better user experience for web applications.

Creating responsive web designs using HTML5 is essential for ensuring that your website adapts well across various devices and screen sizes. To begin, you should utilize the viewport meta tag in your HTML document’s head section. This tag helps control the layout on mobile browsers and is crucial for responsive design:

1. <meta name="viewport" content="width=device-width, initial-scale=1.0" />

Additionally, make use of CSS media queries to apply different styling rules based on the device's characteristics like width and orientation. For example:

@media only screen and (max-width: 600px) { body { font-size: 14px; } }

Incorporating flexbox and grid layouts in your CSS also enhances your responsive design capabilities. Flexbox allows you to align and distribute space among items in a container, while grid layout provides a powerful way to create complex layouts. Here’s a simple example of a flexbox container:

.container { display: flex; justify-content: space-around; }

By applying these techniques, you not only improve the visuals of your site but also enhance the user experience on different devices.