Hi Braedon,
The CWI is a certification, (Certified Welding Inspector) rather than a license. See AWS D1.1 Clause 6.1.4.1 (1)
This certification has to be renewed every 3 years.

As a CWI, I usually work for the owner of the project(building) to represent them on the jobsite during construction, rather than working for a contractor. Although, inspectors can also work for the contractor at times when the contractor does not have their own in-house inspector and the project specifications say that the contractor must provide Quality Control inspection of their work. If that is the case, there will be an additional Quality Assurance inspector who will be hired by the owner to over see the inspection on the project.

My job, most of the time, is to ensure that the welding and structural steel is being installed in accordance with the job specifications and local codes. The job specifications will have all of the codes listed(ie. AWS D1.1) that need to be adhered to during construction from earthwork all the way to the finishing touches.

You can read about this in Clause 6 of AWS D1.1.