There’s not much sense in repeating the immense amount of information about Go here. We’ll leave that to Wikipedia and a few other great sources. The shortest of answers from Sensei’s Library is…
Go is an ancient game which, from its forgotten origins in China, spread first to the rest of East Asia, and then to the entire world. How ancient? Historians aren’t sure; it has a definite history of over 3000 years, but according to tradition Go was invented more than 4000 years ago. The English name comes from the Japanese name Igo, which means “surrounding boardgame”.
For more info take a look at these sites:
Can I play on on-line?
Is the empty triangle bad? Of course you can. Here are a few options:
On-line Go Server – easiest and most accesible Go server. Play right in your browser!
Internet Go Server (PandaNet) – Requires software on your computer or mobile device.
KGS – another popular server that also requires software.