Microsegmentation divides your network into small, isolated segments. Instead of one flat network where any system can reach any other, you create boundaries around individual workloads or groups of related systems.
Traditional segmentation uses VLANs and firewalls between network zones. Microsegmentation goes further, applying firewall-like rules between individual servers or even individual applications. If an attacker compromises one system, they can't easily move to others. Each hop requires breaching another boundary.