What is Jung's synchronicity concept?
Carl Jung believed that certain events occur that are 'meaningful coincidences' but may not be related by causality.
Jung defined synchronicity using terms such as "acausal (notice the use of the word acausal or a-causal, meaning not causing the other) connecting principle," "meaningful coincidence", and "acausal parallelism." He believed that some events may not be connected by causality, but only in meaning. For example, what one sees in a dream and what s/he experiences in real life. One does not cause the other, but there seems to be a meaningful relationship.
Jung used this to justify the paranormal [Roderick, Main (1997). Jung on Synchronicity and the Paranormal. Princeton University Press. p. 1.]. Synchronicity can be used to explain the relationship between two or more psychic and physical phenomenon.
You can find more information on this topic on the Carl Jung website: Carl Jung Synchronicity