What are the advantages in using Terraform or IaC in general?

Full automation: In the past, resource creation, modification and removal were handled manually or by using a set of tooling. With Terraform or other IaC technologies, you manage the full lifecycle in an automated fashion.

Modular and Reusable: Code that you write for certain purposes can be used and assembled in different ways. You can write code to create resources on a public cloud and it can be shared with other teams who can also use it in their account on the same (or different) cloud>

Improved testing: Concepts like CI can be easily applied on IaC based projects and code snippets. This allow you to test and verify operations beforehand