The Buddha is presented in the texts as a physician rather than a prophet: he identifies a condition, its cause, its cure and the treatment. The four statements are usually called the four noble truths.
The condition is dukkha, ordinarily rendered as suffering but closer to unsatisfactoriness, not only pain, but the instability of everything that is sought and held. Its cause is craving, and behind craving, ignorance about how things actually are. Its cessation is possible. The treatment is the eightfold path: right view and intention, right speech, action and livelihood, right effort, mindfulness and concentration, grouped as wisdom, ethical conduct and meditative training, and understood as cultivated together rather than in sequence.
Three characteristics are said to mark all conditioned things: they are impermanent, unsatisfactory, and without a self. The third, anatta, is the most distinctive and the most easily misread. The claim is not that persons do not exist, but that no permanent unchanging essence can be found in or behind the changing processes that make one up. How rebirth works without such an essence is answered by dependent origination, the account of how each state arises in dependence on conditions.
Nirvana is the extinguishing of craving and the ending of rebirth. The tradition is deliberately reticent about what it is, describing it more often by what it is not.
There is no creator in the picture. Gods appear throughout Buddhist cosmology, but they are long-lived beings within the round of rebirth rather than outside it, and cannot grant liberation. Practice for most Buddhists across most of history has centred on ethical conduct, generosity to the monastic community, devotion and the making of merit rather than on meditation, which was until the modern period largely a monastic specialism.