In this blog, we will learn about setup:static-content:deploy command for deploying static content. All Magento 2 extensions are located in app folder, so there is no access to these folders from the browser, but modules have static content like CSS, js and images, so browsers cannot download these static files. So, static content deploy allows you to move the extension files to the pub/static folder to download in the browser.
Magento 2 Static Content Deploy Guide in Details