Good fats are:
polyunsaturated fats and monounsaturated fats(like flaxseed oil,nuts,all antural peanut butter,etc.)
Omega 3 fatty acids(flaxseed oil,fish oil,flameout)
and small amounts of omega six fatty acids(you want to eat more omega 3 and less omega 6.Omega six are healthy,but too much omega six can be unhealthy for you).
And a good saturated fat like coconut oil.
So called "bad fats" are:
Trans fats/hydrogenated oils(most processed foods/junk foods)
And saturated fats.
Many people call saturated fats bad,but I don't think that're as bad as trans fats.Just make sure 100% of your fat intake doesn't come from saturated fats.