Frontend work concerns the user-facing interface and interactions, while backend work handles supporting services, data and application logic. Full-stack work considers how these layers fit together.
Using one language across layers can simplify some interfaces, but it does not remove the need for clear contracts, security boundaries and verification of each layer's behavior.
ELI5
Think of building both a shop's public counter and the systems behind it that manage orders and stock.
For example, a developer may build an agent's chat interface, the service that receives requests and the connection to tools that perform the work.
Does full-stack mean one person must build everything?
No. It describes scope across application layers, which can be shared by a team.
Does using one language eliminate integration problems?
No. Data meanings, permissions and behavior still need to agree across the different components.
