IPA: /ˌɪntəˈpɜːsənl/
KK: /ˌɪntərˈpɜrsənl/
Relating to the way people communicate and interact with each other.
Good interpersonal skills are important for building strong relationships.
Interpersonal is formed from "inter-" (meaning between) and "personalis" (from Latin "persona", meaning person). The word describes relationships or interactions that occur between people.
Think of interactions that happen 'between' ('inter-') 'people' ('persona') — that's what interpersonal means.