How much does Schema code affect SEO and site rankings ?

How much does Schema code affect SEO and site rankings ?

Structured data is added directly to a page's HTML markup. Search engines use structured data to generate rich snippets, which are small pieces of information that will then appear in search results

Go to Google's Structured Data Markup Helper.
Select the type of data that you plan to markup.
Paste in the URL of the page or article that you want to markup.
Highlight and select the type of elements to be marked up.
Continue adding markup items.
Create the HTML.

Go to Google's Structured Data Markup Helper.
Select the type of data that you plan to markup.
Paste in the URL of the page or article that you want to markup.
Highlight and select the type of elements to be marked up.
Continue adding markup items.
Create the HTML.