What is ephemeral storage?

its a temporary storage when the system reboots all the data stored in the ephemeral storage will deleted/cleaned

How to check the available disk space on Linux system

using "df" command we can check the disk free, also use option -h lists human readable i.e #df -h

Any command to list the hidden files in a directory ?

dir /a

How to check the available disk space on Linux system

df -h

what is http and why we need this to be enable in the security group?

HTTP stands for HyperText Transfer Protocol. HTTP is a protocol used for transferring hypertext like HTML pages and images from web servers to web browsers. Security groups act as virtual firewalls that control inbound and outbound traffic to instances. To run a web server on an instance, we need to allow HTTP traffic through the security group so that users can reach your website/application.