WP the_excerpt Function

/*==============================================
*To Displays the post excerpt
===============================================*/
<?php the_excerpt(); ?>

/*===================================================================================
*Use with Conditional Tags
*Replaces the_content() tag with the_excerpt() when on archive or category pages.
=====================================================================================*/
<?php
    if ( is_category() || is_archive() ) {
        the_excerpt();
    } else {
        the_content();
    }
?>

/*======================================================================================
*Control Excerpt Length using Filters
*By default, excerpt length is set to 55 words.
*To change excerpt length to 20 words using excerpt_length filter,
add the following code to functions.php file in your theme:
=======================================================================================*/
<?php
function custom_excerpt_length( $length ) {
    return 20;
}
add_filter( 'excerpt_length', 'custom_excerpt_length', 999 );
?>

/*======================================================================================
*Make the "read more" link to the post
*Place this in a theme's functions.php to make the "read more" link to the post
=======================================================================================*/
<?php
function new_excerpt_more( $more ) {
    return ' <a class="read-more" href="'. get_permalink( get_the_ID() ) . '">Read More</a>';
}
add_filter( 'excerpt_more', 'new_excerpt_more' );
?>