Tags are used to maintain a consistent GraphQL endpoint. You can treat them like pointers or aliases to specific versions, allowing you to swap in new subgraphs in your app without changing your front-end code. By default, subgraph API endpoints are named after the subgraph name and version, so if you update your subgraph to a new version, you’ll need to update your front end to point to the new endpoint. Using tags, you can manage your versions and seamlessly upgrade your subgraph version without having the URL change. In this example, we’ll assume you have already deployed a subgraph with the name and version poap-subgraph/1.0.0. We’ll show you how to create a tag and how to move it to another subgraph version. First, create a tag using the Goldsky CLI and associate it with your subgraph. 
goldsky subgraph tag create subgraph/1.0.0 --tag prod
We’ve now created a new tag called prod. Now our GraphQL endpoint will use the word prod instead of the version number. You should see the new GraphQL endpoint listed in your terminal after running the command. Let’s say you’ve upgraded your poap-subgraph to verison 2.0.0 and want to start querying it with your prod GraphQL endpoint. It’s as simple as creating the tag again on the new version. 
goldsky subgraph tag create subgraph/2.0.0 --tag prod
Like before, you should see the GraphQL endpoint after running this command, and it should be the same as before. Now your queries will be routed to the 2.0.0 version of the subgraph seamlessly