What is morality according to Buddhism? What is good and bad according to Buddhism? Is there good and bad? What is it's cause? What defines good and bad? Why some people think "this same X is bad" and others think "this same X is good"? What's the cause of this difference in thinking "this same X is bad" and "this same X is good"? Are there any suttas talking about all this?
The respective key words for &quot;good&quot; and &quot;bad&quot; in the suttas are &quot;wholesome&quot; (kusala) and &quot;unwholesome&quot; (akusala):

kusala (adj.) [cp. Sk. kuśala] 1. (adj.) clever, skilful, expert; good, right, meritorious.
akusala : (nt.) demerit; sin; bad action. (adj.), unskilful.

&quot;Wholesome&quot; and &quot;unwholesome&quot; here are qualifications for action/kamma. Keeping in mind that, to the Buddha, volition is kamma (see AN 6.63) manifested by body, speech and mind.

“And what, friends, is the unwholesome, what is the root of the unwholesome, what is the wholesome, what is the root of the wholesome? Killing living beings is unwholesome; taking what is not given is unwholesome; misconduct in sensual pleasures is unwholesome; false speech is unwholesome; malicious speech is unwholesome; harsh speech is unwholesome; gossip is unwholesome; covetousness is unwholesome; ill will is unwholesome; wrong view is unwholesome. This is called the unwholesome.
“And what is the root of the unwholesome? Greed is a root of the unwholesome; hate is a root of the unwholesome; delusion is a root of the unwholesome. This is called the root of the unwholesome.
“And what is the wholesome? Abstention from killing living beings is wholesome; abstention from taking what is not given is wholesome; abstention from misconduct in sensual pleasures is wholesome; abstention from false speech is wholesome; abstention from malicious speech is wholesome; abstention from harsh speech is wholesome; abstention from gossip is wholesome; uncovetousness is wholesome; non-ill will is wholesome; right view is wholesome. This is called the wholesome.
“And what is the root of the wholesome? Non-greed is a root of the wholesome; non-hate is a root of the wholesome; non-delusion is a root of the wholesome. This is called the root of the wholesome.
-- Sammādiṭṭhi Sutta, MN 9

(the causes are also repeated and further explained in the Nidana sutta (AN 3.33)).
The above definitions are more general, based on the 3 defilements (greed/lobha, hate/dosa, delusion/moha) but the list of mental states can expand to more specific ones. For example, any of the five hindrances are also understood as unwholesome. In Theravada tradition, the Abhidhamma and Visuddhimagga lists 10  defilements.
In another exposition, the Buddha further distinguishes between four kinds of kamma (see AN 4.235):

&quot;Monks, these four types of kamma have been directly realized, verified, &amp; made known by me. Which four? There is kamma that is dark with dark result. There is kamma that is bright with bright result. There is kamma that is dark &amp; bright with dark &amp; bright result. There is kamma that is neither dark nor bright with neither dark nor bright result, leading to the ending of kamma.

Thus, generally speaking, it is said that wholesome actions are those that lead to a favorable rebirth and lead to nibbāna, whereas unwholesome actions are those that lead to suffering, perdition, hell.

For an interesting read in this subject, see The Roots of Good and Evil by Nyanaponika Thera.