An example of general revelation:
Romans 1:19 because that which is known about God is evident within them; for God made it evident to them. 1:20 For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse.
An example of special revelation:
Exodus 3:13 Then Moses said to God, "Behold, I am going to the sons of Israel, and I will say to them, 'The God of your fathers has sent me to you.' Now they may say to me, 'What is His name?' What shall I say to them?" 3:14 God said to Moses, "I AM WHO I AM"; and He said, "Thus you shall say to the sons of Israel, 'I AM has sent me to you.' "
"Generally" it is known as a "self-evident truth" that there is a God who created everything that exists. Every man knows this, even an atheist (which is why he so strongly protests the idea). However, as great as knowing this is, as one theologian once pointed out, we would not know the name of the Creator unless He had chosen to reveal His name, "Jehovah," to us. We are dependent upon special revelation for that.
And without that special revelation, we could infer a lot of wrong ideas about God simply from general revelation. Case in point, deism. Deism teaches that there is a God who created all things, but when He created the universe, He simply wound it up like a toy, and set it in motion, and let it go to do its own thing. Such is a logical inference, as we observe a world of natural laws that apparently cause all things to work the way they do. But, such a thing would contradict special revelation, as by special revelation we learn that God didn't simply set the world in motion and let it go, but rather, God is intimately and actively involved in every aspect of everything that happens in the creation. The world isn't simply spinning because of natural laws, but because God is making it spin.
To sum up: General revelation teaches us a lot of things about truth, but is limited in what it can teach us. Indeed, without special revelation to guide us, we might deduce from it things that are contradictory from the way God actually sees things.
I hope that helps.