According to the Buddha, what is samsara made of?
- Karma?
- All the Buddhist realms of existence?
- You're momment by moment mind and body experiencial arisings as they happen?
- Isn't samsara what arises when you meditate satipatthana?
Samsara is the sense of a "self-being" caused by ignorance & craving.
Bhikkhus, this saṁsara is... beings roaming and wandering on hindered by ignorance and fettered by craving.
Suppose, bhikkhus, a dog tied up on a leash was bound to a strong post or pillar: it would just keep on running and revolving around that same post or pillar.
So too, the uninstructed worldling … regards form as self … feeling as self … perception as self … volitional formations as self … consciousness as self…. He just keeps running and revolving around form, around feeling, around perception, around volitional formations, around consciousness. As he keeps on running and revolving around them, he is not freed from form, not freed from feeling, not freed from perception, not freed from volitional formations, not freed from consciousness. He is not freed from birth, aging, and death; not freed from sorrow, lamentation, pain, displeasure, and despair; not freed from suffering, I say.
But the instructed noble disciple … does not regard form as self … nor feeling as self … nor perception as self … nor volitional formations as self … nor consciousness as self…. He no longer keeps running and revolving around form, around feeling, around perception, around volitional formations, around consciousness. As he no longer keeps running and revolving around them, he is freed from form, freed from feeling, freed from perception, freed from volitional formations, freed from consciousness. He is freed from birth, aging, and death; freed from sorrow, lamentation, pain, displeasure, and despair; freed from suffering, I say.
In short, samsara is all of the people of world (except for the Noble Ones) running & wandering around searching &/or completing for things driven by the various cravings.
Samsara is the cycle of birth and death of the individual. This definition works for both Buddhism and Hinduism, in Pali and Sanskrit.
To be precise, it is the repeated occurrence of the arising and ceasing of the sentient being (especially with respect to self-identity or individuality). Here's where it is specific to Buddhism.
The illusionary self is simply an idea, a thought in the mind. This is implied in the notion of "I am the thinker" in Snp 4.14 and in the nidana of jati in dependent origination.
Dependent origination explains how the sentient being (including the self) arises, dependent on craving, the mind-body phenomena, and ultimately dependent on ignorance.
Transmigration (samsara) has no known beginning. No first point is found of sentient beings roaming and transmigrating, shrouded by ignorance and fettered by craving. For such a long time you have undergone suffering, agony, and disaster, swelling the cemeteries. This is quite enough for you to become disillusioned, dispassionate, and freed regarding all conditions.”
SN 15.1
You are asking what is samsara made of like in what is cake made of ? The answer is simple Samsara is made of six senses and their contacts i.e. tongue contact resulting in taste , nose contact resulting in smell, ear contact resulting sound , eye contact resulting in sight , body contact resulting in touch , mind contact resulting in mental formations.
That is all there is.
There is ignorance and within this realm of ignorance there is karma ,realms of existence and experiences.