Metadata as the name suggest is about data. Meta data plays an important role in search engine optimization as it serves as the source for search engines for the information they are looking for on web pages. Without metadata the ability to drive consumers to a particular website is particularly weakened.
Almost all metadata is hidden from the view of the visitors and the customers. They work in the background on the HTML of the web pages. These metadata communicate with the search engines which crawl the web pages,they provide the information that the search engines are looking for with respect to particular search query.
The most basic metadata are the meta tags. Meta tags looks like the following example
Meta description, meta keywords and meta robots are the normally used meta data. Description is a short description of a particular page related to the information it carries. Meta keywords are the keywords for which the particular page designed to rank for.
Title tags are the most important for SEO. They carry the most relevant keywords, product name, or article name, and end with the name of the site. Image tags are primarily used for identifying the url of an image. For SEO, the alternative attribute is used to apply some textual context to an otherwise unreadable element for impaired customers and search engines.
Alternative attribute is an important image attribute that serves the needs of impaired customers. They also act as keyword relevance in SEO that is useful in image search results.
There are many other forms of metadata relevant to SEO, but these are the most commonly used tags and attributes.
