reversible/irreversible processes

[Sol Lee 2H]

this may sound very basic at this point but,

What exactly is reversible/irreversible in a reversible/irreversible process?

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[Annie Qing 2F]

Irreversible processes are ones that happen suddenly (e.g. gas being released into a vacuum) whereas reversible processes are done over a theoretically infinite amount of time because the change happens in infinitesimally small parts. In a reversible process, the system is in equilibrium throughout the entire change and energy from work is maximized (most efficient).

Hope this clears (at least some) things up!