CI/CD Azure Synapse Workspace with Azure Devops

Dear all, 

I am working on CI/CD between Azure Synapse Workspace with Azure Devops. 

I have source code from someone else who work on this project before and it works well and I try to understand it and create my own project on it. right now, I have issues of the deplolyment stage: 

1.  under release, people usually add Git Repos in Artifacts, but in my case, I have a build synapse workspace before add Git Repos. 

So my question: why do we need to Build synapse workspace before add Git Repos?  

below is the source code for Build synapse workspace:

Could you tell me why do we need this?

2. in my Repos, we have develop branch (for CI) and prod branch (for CD). Under my Repos in develop branch, I have two yaml files which relates with pipeline in Pipelines. I have no idea how does it generate. Will these two yaml files will generate automatically when I create pi 

Many thanks, 

Joan