The Four Paramattha Dhammas - Citta and Cetasika

There are two kinds of conditioned nāma: citta (consciousness) and Cetasika (mental factors arising together with consciousness). They are nāmas which arise because of conditions and fall away again.

As regards citta, citta knows or experiences an object. Each citta must have its object of knowing, in Pāli: ārammana. Knowing or experiencing an object does not necessarily mean thinking about it. The citta which sees has what is visible as object; it is different from the cittas which arise afterwards, such as the cittas which know what it is that was perceived and which think about it. The citta which hears (hearing-consciousness) has sound as its object. Even when we are sound asleep and not dreaming, citta experiences an object. There isn't any citta without an object. There are many different types of citta which can be classified in different ways.

Topic 174