Plugins

plugins_url()
    
//-> https://compendium.xyz/wp-content/plugins
    
echo '<img src="' .esc_url( plugins_url('images/icon.png', __FILE__ ) ). '" >';

//-> <img src="https://compendium.xyz/wp-content/plugins/my-plugin/images/icon.png">

Admin

admin_url()

//-> http://compendium.xyz/wp-admin/
Generate URL to admin "Review" page and use 'https':
echo admin_url('edit-tags.php?taxonomy=review', 'https');

//-> https://compendium.xyz/wp-admin/edit-tags.php?taxonomy=review

Site

site_url()
    
// Notice the absence of trailing slash:
//-> http://compendium.xyz
site_url('/blog/','https')

//-> https://compendium.xyz/blog/

Home

home_url()

// Notice the absence of trailing slash:
//-> http://compendium.xyz

home_url('/')

// Trailing slash must be explicit
//-> http://compendium.xyz/

home_url($path='/', $scheme=https)

//-> https://compendium.xyz/

home_url($path='blog', $scheme=relative)

//-> /blog

Content

content_url()

// Notice the absence of trailing slash:
//-> https://compendium.xyz/wp-content

Upload

wp_upload_dir()

//-> Array(
//      'path' => '/srv/www/wordpress/wp-content/uploads/2014/05',
//      'url' => 'http://compendium.xyz/wp-content/uploads/2014/05',
//      'subdir' => '/2014/05',
//      'basedir' => '/srv/www/wordpress/wp-content/uploads',
//      'baseurl' => 'http://compendium.xyz/wp-content/uploads,
//      'error' =>
//    )

Child theme

get_stylesheet_directory_uri()

<img src="<?php echo get_stylesheet_directory_uri(); ?>/images/logo.png" alt=""/>