Existence, being, actuality are closely related in meaning but not always interchangeable.
Existence is the inclusive term which designates the state or condition of anything regarded as occurring in space or time, as distinct and apart from all other things, and as having a nature or substance of its own.
The opposite of existence is its complete negation nonexistence.
Being, when it denotes existence, adds varying implications. Sometimes it implies life, consciousness, or personality. Sometimes it implies fullness or completeness of existence and absence of imperfection.
Sometimes it suggests the complex of qualities or characteristics that constitute the nature of a person or a personified thing.
Actuality as a synonym of existence stresses realization or attainment; it usually implies opposition to possibility or potentiality.