Full definition
A reverse proxy is the mirror image of a regular ("forward") proxy. A forward proxy sits between a client and the internet — it hides the client's IP from destination servers. A reverse proxy sits between the internet and a server — it hides the server's IP from clients. Cloudflare is a reverse proxy. Nginx in front of your app is a reverse proxy. Akamai is a reverse proxy.
Why this matters for scraping: when you're trying to scrape a site, you're actually talking to its reverse proxy first. The CDN can do TLS termination, caching, rate limiting, IP banning, and bot detection — all before your request ever reaches the origin server. So when people say "Cloudflare blocked me", what they mean is "Cloudflare's reverse proxy blocked me before Cloudflare's client's server ever saw the request."
Practical implication: most anti-bot battles are with reverse proxies (CDN-level), not with the actual website. Working out which CDN a target uses is the first step in choosing your bypass approach.