Buddhism begins with the Four Noble Truths, that I paraphrase as:

All life on earth incurs added and unnecessary suffering
Due to our human desires becoming inflamed (by hatred, greed, delusion, and ignorance).
One can stop contributing to this unnecessary suffering
Through the eight-fold path.

"Life" above probably includes all things; (just after his enlightenment and attainment of Buddha nature, Buddha purportedly said something like "it is wonderful that all things, and all beings, are Buddha nature").
Instead of the word"suffering" above, various teachers use "anguish", "dissatisfaction", or similar alternative words.
The parenthetical phrase "(inflamed ... )" could presumably include the seven deadly sins; others argue that this suffering is due to our human delusions (ego) that in turn cause hatred, greed, ignorance, and other sins.

Buddhism addresses how to end suffering, rather than metaphysical or teleological issues such as the nature of things, or why things are as they are. The noble truths offer a diagnosis of what is wrong and prescribe what to do; Buddha's later Heart Sutra and Metta Sutra are similar, but offer more detail, about a page each. The Heart Sutra addresses form and emptiness, and mind and consciousness. The Metta Sutra addresses kindness and compassion, You can find each Sutra easily on the web.

Other principles of Buddhism, in addition to the possibility of ending suffering, are impermanence, emptiness, and causation. Impermanence and emptiness imply that we have no permanent self or ego. Instead everything changes, including our egocentric notions of who we are. Causation, or karma, means that everything happens due to prior causes and conditions. Three gates to liberation include Emptiness/inter-being (egolessness, no self), Signlessness/notionlessness (everything changes, impermanence). and Wishlessness/non-craving (ending dissatisfaction, desire and aversion).

Buddhist practice engenders awakening, and enlightenment is central to Buddhism. Buddhist lore includes awakening to unsurpassed, complete, perfect enlightenment, e.g., Buddha's enlightenment. However, most Zen students experience many minor awakenings over the years, as well as a subtly increasing sense of transparency within ourselves and our practice, and a sense of being increasingly permeated by the very sweet energy of nature, nirvana, or emptiness. Mindfulness and Meditation are tools to approach the eight-fold path.

There is no single source in Buddhism. Instead each country and tradition has separate organizations, and they are quite diverse. Some are faith-based, like western religions. Probably the most notable current sources are the Dalai Lama (Tibet), who takes "kindness" as the core of Buddhism and happiness as the core of life, and Thich Nhat Hahn (French/Vietnamese); see my review of "The Heart of Buddha's Teachings" by Hahn.