Traditional cloud applications wait for a server before confirming many actions. Local-first applications instead write to a local data model immediately and synchronize in the background. The result is lower perceived latency and useful offline behavior.
What matters in practice
The difficult part is conflict resolution. Teams need explicit rules for merging concurrent edits, preserving intent, and communicating synchronization state without exposing implementation details to users.
A useful rule
Local-first is not automatically the right architecture. It adds complexity, but it is compelling for creative tools, field work, collaboration, and any workflow where connectivity should not control productivity.