See: https://httpd.apache.org/docs/current/mod/mod_proxy.html

Enable the mod_proxy and mod_http modules in Apache’s httpd.conf file.

Apache mod_proxy library: The ability to use Apache as a reverse proxy is provided through a shared library named mod_proxy.so. This module is not enabled by default, so you must edit Apache’s httpd.conf file to enable it. You also need to enable Apache’s mod_proxy_http.so shared library.

Enable Apache mod_proxy: Uncomment the appropriate line in Apache’s httpd.conf file to enable the Apache mod_proxy and mod_proxy_http modules:

### Enable LoadModule entry for Apache mod_proxy and mod_proxy_http ###
#LoadModule proxy_fcgi_module modules/mod_proxy_fcgi.so
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
#LoadModule proxy_scgi_module modules/mod_proxy_scgi.so

Example of Reverse Proxy/Gateway in apache virtual hosts file.

Reverse Proxy
ProxyPass "/foo" "http://foo.example.com/bar"
ProxyPassReverse "/foo" "http://foo.example.com/bar"