A hit is a request for a file on a web server - any request for any file, so opening one HTML page which contains 10 images and 1 Flash animation will register as 12 hits (1 HTML file + 10 + 1). Hits are not the same as visits, contrary to what some web marketing schemes would imply. 10,000 hits may sound impressive, but if every page loads 100 images then 10,000 hits translates to less than 100 actual visitors.
HTML code refers to the markup language that is used to build web pages. The term "code" can a misleading here as it is normally used to refer to programming languages. HTML is not a programming language.