a struct in a function parameters

[Anddos]

ive started to learn c++ for halflife modding , and ive come across something which is puzzling me .

void NET_CALLBACK ListResponse( struct net_response_s *response );

now have can you have a function like this
with 2 function names plus saying struct in the parameters..
and ive seen struct within a class..all this is new to me
and the programmers of this mod sdk was able to use
CHudServers *g_pServers; /////////////// -> on its members without
making CHudServers *g_pServers = new Chudservers...
can someone clear some of this up :P