Features of Mental States

Intentionality: This is the ‘aboutness’ or ‘directedness’ of mental states. They often have a content which they refer to or are about - such as when an individual believes in a particular idea or desires a specific outcome.
Privileged access: Holders of mental states have a certain privileged or unique access to them, usually unavailable to others. Depending on the theory, this access may be infallible, incorrigible, or simply more direct than the access others might have.
Phenomenal Properties: Some mental states have subjective experiences, known as phenomenology, that come along with them. For example, sensations such as pain or perceptions such as seeing a particular colour, come with a certain ‘what it’s like’ feeling.

Physicalist view: According to this understanding, mental states are entirely physical and are related to brain states in various ways - they can be identical to brain states, realised by them, or supervenient upon them.
Dualistic view (Cartesian Dualism): This viewpoint holds that mental states are entirely non-physical and exist separately from the body. These mental states interact with physical bodies in the world but remain fundamentally different from them.

Propositional attitudes: These are attitudes that one can take towards a proposition, such as believing it, desiring it, hoping it, fearing it etc. Each involves a mental state (belief, desire, hope, fear etc.) and a content (the proposition).
Sensations/feelings: Emotions and sensations like fear, joy, pain etc., are often considered to form distinct types of mental states. These mental states tend to have a strong phenomenology and may not always incorporate any explicit propositional content.
Perceptual experiences: These are direct experiences of the world, such as seeing a bird or hearing a sound. These experiences are usually approximately veridical representations of the external world.