In the HEAD element, a "title tag" is a type of HTML tag that looks like this:
<title>Your web page title</title>
that is one of the most crucial codes or elements for indicating to users and search engines what the page's title and subject are.

The title tag, also known as the page title, is an essential element of on-page SEO. It serves as a short description of what the webpage is about and is displayed in the search engine results page (SERP) as the clickable link to your website. A well-written title tag can improve click-through rates, enhance user experience, and ultimately boost website ranking on Google and other search engines.

The title tag is an integral part of on-page SEO because it helps search engines understand the content of your webpage. Search engines use title tags to determine the relevance of the page to the user's search query. If the title tag is well-written and relevant to the search query, it is more likely to appear in the top search results.

Here are some tips for optimizing the title tag for SEO:

1. Keep it concise and descriptive: The title tag should be no longer than 60 characters, including spaces, and should accurately describe the content of the page. It should also include the primary keyword for which you want to rank.

2. Avoid duplicate title tags: Each page on your website should have a unique SEO-friendly title tag. Duplicate title tags can confuse search engines and affect your website's ranking.

3. Use branding elements: an SEO-friendly title tag should also include branding elements, such as your brand name or website name, preferably at the end of the title tag. This helps to improve brand recognition and increase click-through rates.

4. Don't overstuff keywords: While it's essential to include the primary keyword in the title tag, avoid stuffing it with too many keywords. This can appear spammy and hurt your website's ranking.

5. Write for the user: Remember that the title tag is also displayed on the search engine results page. Therefore, it's crucial to write it in a way that will entice users to click through to your website. The title tag also should be written for providing a clear idea of what they can expect to find on the page.

Bad Title Tag Example: "Welcome to Our Website"

This title tag is vague and doesn't provide any information about the content of the page. It also doesn't include any relevant keywords, which makes it difficult for search engines to understand the purpose of the page.

Good Title Tag Example: "Affordable Web Design Services - A Shop for All Your Needs"

This title tag is concise and descriptive, providing information about the services offered on the page. It includes the primary keyword "web design services" and is written for the user, making it more likely to attract clicks.

By creating SEO-friendly title tags for each page on your website, you can attract more organic traffic, and ultimately drive more conversions.

In conclusion, the title tag is a vital element of on-page SEO that can significantly impact your website's ranking on Google and other search engines. By optimizing the title tag for SEO and writing it for the user, you can improve click-through rates, enhance user experience, and ultimately boost your website's visibility in search results.