I don't understand the bellow two sentences' meaning

Protocol
1

I don’t understand the below two sentences meaning :

**PAC mode**: All http/socks data is forwarded through the proxy server. 
Only software that supports socks5 or uses system proxy can use Shadowsocks (general browsers use system proxy by default).

**Global mode**: does not require the application to follow a specific operating system platform, 
but simply passes the packet without caring about the application protocol (such as FTP, HTTP, and NNTP requests).
2

PAC mode only work for browsers and applications that can be configured to use the proxy. Global mode send all requests from all applications.