A web server is software and hardware that uses HTTP (Hypertext Transfer Protocol) and other protocols to respond to client requests made over the World Wide Web. The main job of a web server is to display website content through storing, processing and delivering webpages to users.

To set up a basic web server on Ubuntu, you can use Apache, one of the most widely used web servers. Here's a step-by-step guide:

• Install Apache::
  

  Open a terminal on your Ubuntu system. Update the package index:

  sudo apt update
      

  Install the Apache package:

  sudo apt install apache2

• Configure Firewall (if applicable):

  If you have a firewall enabled (like UFW), you'll need to allow incoming traffic on port 80 (HTTP) so that external users can access your web server:

  sudo ufw allow 'Apache'
  

• Verify Apache Installation:

  Once Apache is installed, it should start automatically. You can verify its status using:

  sudo systemctl status apache2
  

• Access Default Page:

  Open a web browser and enter your server's IP address or hostname in the address bar. You should see the default Apache web page, indicating that Apache is working correctly.

• Serve Your Own Content:

  By default, Apache serves files from the /var/www/html directory. You can place your website files in this directory to serve your own content.
  Alternatively, you can create virtual hosts to host multiple websites on the same server. Each virtual host can have its own directory for serving content.

• Manage Apache: Apache's main configuration file is located at /etc/apache2/apache2.conf. Additional configuration files are stored in the /etc/apache2/sites-available directory. You can use commands like sudo systemctl start apache2, sudo systemctl stop apache2, and sudo systemctl restart apache2 to manage the Apache service.
• Secure Your Web Server: Consider implementing security measures such as SSL/TLS encryption, HTTP authentication, and access controls to protect your web server and its content.

That's it! You now have a basic Apache web server set up on your Ubuntu system. You can further customize and expand its functionality by installing additional modules and applications as needed.