Phishing sites are sites which claim to be a popular site but in reality they are trying to steal you credit card data or worse still, transfer money from your bank account.
To protect you self, you can use the Netcraft Anti-Phishing Toolbar.
I have used this on Firefox and it works well and blocks all the dangerous sites even if you accidently click on them. It also shows a risk rating for any web site you visit.
Its a must for every for every web user.