This code

-> Spins up an instance

-> Attaches a created EBS volume at launch through user data

-> The user data is defined in the file cloudinit.tf Script files are called in cloudinit.tf. The output of the latter is referenced through user-data in instances.tf

 -> The script volumes.sh will allow us to reuse the same EBS volume for another instance even if the instance it was attached to previously has been terminated