Is there a difference between Enlightenment and Nibbana?
Enlightenment is the insight knowledge that cuts through & extinguishes the mind's defilements (cravings) of greed, hatred or delusion.
Nibbana is final peace or coolness that is experienced after the 'fires' of greed, hatred & delusion have been extinguished.
Enlightenment is the cause which allows (the pre-existing but hidden) Nibbana to be experienced.
This process is described in the Anatta-Lakkhana Sutta
Seeing (impermanence, unsatisfactoriness & not-self) thus , the well-instructed disciple of the noble ones grows disenchanted with form, disenchanted with feeling, disenchanted with perception, disenchanted with fabrications, disenchanted with consciousness. Disenchanted, he becomes dispassionate. Through dispassion, he is fully released. With full release, there is the knowledge, 'Fully released.'
The 'seeing thus' is enlightenment. 'Becoming dispassionate' (end of craving) is Nibbana. 'Fully released' is liberation (which is also Nibbana). The knowedge 'fully released' is enlightenment, in clearly knowing the end of craving is Nibbana.
The real problem is that both concepts are poorly defined in the Pali Canon. If you are a Westerner, then you want a more psychologically sophisticated answer. After 50 years of mindfulness practice, I only offer the following answer: Enlightenment or nibbana can be viewed as that fullest possible attunement with the Bodhicitta, which is an innate and ancient intelligence that has developed within you and is the product of a long evolution of intelligent consciousness that is deeply loving. Complicated? Absolutely. But an intellectual definition won't help much anyway. However, the mindfulness of breathing allows your Bodhicitta to function (if only unconsciously at first). More advanced forms of mindfulness meditation are somewhat like "focusing" as defined Eugene Gendlin.