What's a proxy server?

In linux, you can check the proxy settings by using the command

$ env | grep proxy

or you can use the following commands

$echo $HTTPS_PROXY
$echo $HTTP_PROXY

$echo $http_proxy
$echo $https_proxy

If it doesn't show anything, then the proxy is not set.

Otherwise, you can unset them using the following commands.

$ unset  https_proxy
$ unset http_proxy