An API gateway is a layer 7 (application layer) tool that routes incoming requests to the appropriate microservice for facilitating data exchange between separate applications, while providing advanced routings and traffic management capabilities such as path-based routing, canary deployments, and observability features. A load balancer is a layer 4 component that distributes and manages incoming requests across multiple instances of a microservice, improving availability and handling more traffic. Edge Stack, Traefik, and NGINX are popular tools for implementing an API gateway and load balancer in a Kubernetes environment, each with unique advantages such as advanced routing capabilities, security features, scalability, and ease of use. When choosing an API gateway, consider factors such as functionality, performance, cost, ease of use, dev environment, scalability, security, monitoring, and compatibility with your existing system.