Forward proxy: sits in front of clients, filters outbound traffic. Reverse proxy: sits in front of servers (WAF, load balancer). Transparent proxy: intercepts without client config. SOCKS proxy: generic application-layer proxy.
Forward proxy = protects clients/monitors egress. Reverse proxy = protects servers. SSL inspection proxy decrypts/re-encrypts HTTPS — requires installing a CA cert on clients. Split tunneling proxies route some traffic through proxy, rest directly.