Site pages are primarily used for the content in a site. Site pages come in two types
When a user customizes a site page, the template for the page is then stored in the content database.
Site pages can’t have code behind or inline code and Can be deployed using a sandbox / farm solution
Site pages Support web parts. Deployed only on specific sites and Can be deployed by site collection administrator/end user.
Open the sharepoint site and click on settings Button and click on Add page
Enter the site page name and Create