1000 proxies

Someone please explain to me what these proxies are.

Google proxies instead of waiting 3 hours for someone to answer for you next time.

In computer networks, a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers.Today, most proxies are web proxies, facilitating access to content on the World Wide Web and providing anonymity.

For simplicity's sake, proxy servers are a "middle man" between your computer and another system, except the middle man won't grass on you and leave you anonymous.
Here, we use proxies to repeatedly enter different passwords to see if they work using a program.(Like guessing a password for someone's account but automated)

IS there a reason you have to switch proxies?
Does it only allow a certain amount of attempts before you need to change proxies?

Thank you very much for sharing!