The cosmological argument for God's existence is really very simple:
Premise 1: Everything that begins to exist requires a cause.
Premise 2: The universe began to exist.
Conclusion: The universe has a cause.
Following this logic, you're about two steps away from concluding that, therefore, in the beginning, God created the heavens and the earth. Atheists, of course, don't like this, and so they try to turn the argument back on God. What, they ask, created Him?
This question is flawed by the first premise. The initial premise is that everything that begins to exist has a cause. Or, to put it as John does, "All things were made through Him, and without Him nothing was made that was made." Now, if nothing was made that has been made without Him, He obviously cannot have been made. To put it another way, God does not need a cause because there was never a time when He did not exist. The sceptic's objection is refuted by a simple reading of one of the most famous books in the Bible.
There are two important takeaways from this. 1. God exists. 2. It's really rather important to learn about Him, lest you look a little bit silly when you argue against Him.