These are both similar terms typically referred to by manufacturers to describe a final stage of charge. One could say the charger turns off or on as needed to keep the battery charged. Others may say the charger pulses states to maintain the battery at 100%.
The real subtle discrepancy is that pulse chargers are a marketing tool used by the "as seen on TV" types to promote a device that isn't powerful enough to be a charger or maintainer but is marketed as a device to desulphate batteries by using an ocillating current to break down the lead sulphate build up on plates. The concern is that if you'd charged your batteries properly in the first place they wouldn't need such a device and by purchasing a CTEK charger you wouldn't need one anyway.