The meta title is the name of a HTML document. It is stored in the head data of the document. It can only appear once in the entire document. Optimizing meta titles for better rankings is an important part of SEO. Alternative descriptions of meta titles are the title tag, or page title. The addition "Meta" is technically incorrect, because it is not actually a meta-description. However, in practice, the title counts as part of the meta data in the header of a website.
Usually, the meta title consists of both main keywords and the firm or brand description, potentially also the area where the firm is based. Whether the location is included in the title depends on whether the website is optimized locally or not.
The meta title is an important element for both user and search engine. It is displayed in the title page of the browser and in the open tabs. Moreover, the Meta title forms the headings of entries in search engines, and is, for example in Google, shown in blue on the SERPs. A few social networks use the page title as a heading, for example when users share links.
That’s why this meta tag is extremely relevant: the Google algorithm calculates the value of the keywords in the meta tag very highly. This is also applies to other search engines.
The Meta Title is considered as one of the so-called low hanging fruits, because by adapting it, rankings can easily be improved. This is different to meta-descriptions which which no longer have ranking relevance. From a SEO perspective, a good title should only be used once for a website, and should contain the following elements:
The following aspects should be avoided:
Such problems with the Meta title can be identified in the Webmaster-tools under HTML improvements.
The title shouldn't contain more than 70 characters. However, after various Google updates, the interpretation of the Title Tag has changed. Tests  have shown that having a solid number of characters will no longer determine whether a title will be shortened. Instead, Google works out the pixel length of every single letter and adds it up to a total length. If the pixel length exceeds the maximum, the title is being shortened and trailed with “...”.
Google doesn’t necessarily make use of the Title Tag, but also replaces this with different information if the usability is expected to improve. If a title includes “Click here”, it is probable, due to the "otisredding" update, that instead of a title, other text elements of the website will be displayed, which suit the user’s search term better. 
The Google updates “tomwaits” and “TopOfTheRock” have lead to the fact that Title Tags are not only being shortened, but are in some cases completely replaced with other parts of the website  if the set Meta Title Tag is too long. Future changes are certainly to be expected.
If the website is registered in the Open Directory Project (“DMOZ”), it is possible that Google may have replaced the Title Tags with DMOZ data .
However, the project is no longer continued today and Google therefore doesn't take any more data from the DMOZ project. The tag NOODP has lost its use.
The meaning of the meta title for the Search Engine Optimization can be considered as highly standardized. It is considered to be the most important ranking signal next to the content and should be chosen wisely. When creating a meta title, three aspects are very important: It should describe the content briefly and concisely, cover the most important keywords and encourage you to click. The Meta Title is therefore directly related to OnPage optimization and is thus associated with keyword analysis as well as the user experience and one of the most important key figures in web analysis - the CTR.
It should be noted that all data displayed in the search engines are also saved on the Google server. If changes are made to the title, these won't be visible immediately. It can take a few days until the title is visible in the SERPs. How quickly the new page title is adopted depends, among other things, on how often the website is crawled.