What does the azd up command do?
The azd up command comes from the Azure Developer CLI, and takes care of both provisioning the Azure resources and deploying code to the selected Azure hosts.
The azd up command uses the azure.yaml file combined with the infrastructure-as-code .bicep files in the infra/ folder. The azure.yaml file for this project declares several "hooks" for the prepackage step and postprovision steps. The up command first runs the prepackage hook which installs Node dependencies and builds the TypeScript files. It then packages all the code (both frontend and backend services) into a zip file which it will deploy later.
Next, it provisions the resources based on main.bicep and main.parameters.json. At that point, since there is no default value for the OpenAI resource location, it asks you to pick a location from a short list of available regions. Then it will send requests to Azure to provision all the required resources. With everything provisioned, it runs the postprovision hook to process the local data and add it to an Azure Cosmos DB index.
Finally, it looks at azure.yaml to determine the Azure host (Functions and Static Web Apps, in this case) and uploads the zip to Azure. The azd up command is now complete, but it may take some time for the app to be fully available and working after the initial deploy.
Related commands are azd provision for just provisioning (if infra files change) and azd deploy for just deploying updated app code.