Use content from one page in another template

Assuming you have the following pages:

1. Home
2. About us that has a slug of about-us

And you want to display the content of the About us page into the Home page.

<?php 
    $about_us = get_page_by_path('about-us'); // supply the page slug; i.e. about-us

    $about_us_content = get_the_content($about_us->ID);
?>

<div><?php echo $about_us_content ; ?></div>

Alternatively, you can use the get_page_by_title to retrieve the post using its page title