WordPress theme directory structures and it’s files

WordPress theme home directory:
Wordpress HOME/wp-content/themes/yourTheme/

Directories inside the theme directoy:
Wordpress HOME/wp-content/themes/yourTheme/images
Wordpress HOME/wp-content/themes/yourTheme/inc
Wordpress HOME/wp-content/themes/yourTheme/js
Wordpress HOME/wp-content/themes/yourTheme/languages
Wordpress HOME/wp-content/themes/yourTheme/layouts

Files inside the theme directory:
Wordpress HOME/wp-content/themes/yourTheme/404.php
Wordpress HOME/wp-content/themes/yourTheme/archive.php
Wordpress HOME/wp-content/themes/yourTheme/comments.php
Wordpress HOME/wp-content/themes/yourTheme/conents.php
Wordpress HOME/wp-content/themes/yourTheme/content-aside.php
Wordpress HOME/wp-content/themes/yourTheme/content-single.php
Wordpress HOME/wp-content/themes/yourTheme/footer.php
Wordpress HOME/wp-content/themes/yourTheme/functions.php
Wordpress HOME/wp-content/themes/yourTheme/header.php
Wordpress HOME/wp-content/themes/yourTheme/image.php
Wordpress HOME/wp-content/themes/yourTheme/index.php
Wordpress HOME/wp-content/themes/yourTheme/license.txt
Wordpress HOME/wp-content/themes/yourTheme/no-results.php
Wordpress HOME/wp-content/themes/yourTheme/page.php
Wordpress HOME/wp-content/themes/yourTheme/rtl.css
Wordpress HOME/wp-content/themes/yourTheme/search.php
Wordpress HOME/wp-content/themes/yourTheme/searchform.php
Wordpress HOME/wp-content/themes/yourTheme/sidebar.php
Wordpress HOME/wp-content/themes/yourTheme/single.php
Wordpress HOME/wp-content/themes/yourTheme/style.css

The most important file is the index.php, it calls all other files to compose the web page you will see on the browser.