What are the essential META tags I should be using in every project?

Here are the Meta tags that I use for my professional work, and why I use them:

The description meta tag is great for describing your site to the search engine which is great for SEO (search engine optimization) and for the visually impaired as screen readers will read this out to them. It is also the description that is shown underneath the url displayed in a search engine.

<meta name="description" content="This is a simple website about cats">

The keyword meta tag is great for SEO because when a user types in one of these keywords, they may find your site, you should change the keywords for each page though, and make sure they are specific!

<meta name="keywords" content="cats, feeding cats, funny cats">

The viewport meta tag is essential for any site that utilizes responsive design because it ensures the layout of the site will be set to a scale of 1:1 for their current device. Which is great for setting up the proper layout for them.

<meta name="viewport" content="initial-scale=1">

Finally the title tag (though not an actual meta tag) is useful for displaying the name of current page to the user, and is great for both the visually impaired (for screen readers) and the SEO for better website ranking.

<title>Homepage | Basic Website</title>

Well those are the meta tags that I at least believe are essential, I recommend you look up the meta tags and determine for yourself what you believe needs to be on your site! Good luck and have fun coding!