Load balancing for HTTP-based traffic helps distribute incoming requests across multiple servers to ensure reliability, availability, and performance of web applications. Here’s how it works:

1. Traffic Distribution: When users send HTTP requests, the load balancer receives these requests and distributes them across a pool of backend servers (instances). This prevents any single server from becoming overwhelmed by traffic.

2. Health Checks: The load balancer regularly checks the health of backend servers. If a server is detected as unhealthy, the load balancer will stop sending traffic to it and redirect the requests to healthy servers, ensuring minimal downtime.

3. Session Persistence: Some load balancers support session persistence (also known as sticky sessions), where a user’s session is consistently directed to the same server. This can be important for applications that rely on user session data.

4. SSL Termination: The load balancer can handle SSL/TLS encryption, decrypt the incoming traffic, and then forward it as plain HTTP traffic to the backend servers. This reduces the workload on backend servers and simplifies certificate management.

5. Scalability: By distributing traffic across multiple servers, load balancing enables horizontal scaling. When demand increases, new servers can be added to the pool, and the load balancer will automatically distribute traffic to the new instances.

6. Geographic Load Balancing: Some advanced load balancers can direct traffic to the nearest data center or region based on the user's location, reducing latency and improving user experience.

Overall, HTTP-based load balancing ensures that web applications can handle more traffic, recover from failures, and provide a consistent and responsive user experience.