display custom plugin view on front end inside template body

In your plugin class (e.g. MyPlugin), add public static function, returning some content:

public static function my_plugin_output() {
    // Build your content
    $output="<div>";
    $output .= 'This is a text to display.';
    $output .= '</div>';
    return $output;
}

Once your plugin is activated, add this line to any template, you want the plugin content to appear:

<?php if (class_exists('MyPlugin')) echo MyPlugin::my_plugin_output(); ?>