Load Balancer
In plain terms
A traffic director that spreads incoming requests across multiple servers.
Going deeper
It sits in front of a pool of servers and routes each request to a healthy one, preventing any single machine from being overwhelmed. It improves availability (route around dead servers) and lets you scale horizontally by adding more machines behind it.
Under the hood
Layer 4 (transport) vs. Layer 7 (application) balancing enables different routing; health checks, session affinity, and SSL termination are common features.
Examples
AWS ELB/ALB, NGINX, HAProxy, round-robin, least-connections strategies.
Think of it like...
Like a host at a busy restaurant seating arrivals across all the open sections so no single waiter is buried while others stand idle.