Git groups objects into packfiles when transferring or compacting repository data. A separate index helps locate objects within the pack, and delta compression can encode one object relative to another.
Packfiles reduce size and network overhead, but a distributed host must transfer and coordinate durable writes of those packs. Large-scale replication can therefore make write latency sensitive to slow replicas.
ELI5
A Git packfile is a compressed container that stores many Git objects together for efficient transfer and storage. It can represent one object as the difference from another instead of repeating similar data.
For example, a server can send one pack containing the objects needed for a clone rather than thousands of small files. The compact format saves space and network overhead, although distributed hosts still need to write and replicate the pack reliably.
