Planned tests are determined before looking at the data, and post hoc tests are conceived only after looking at the data (though the term "post hoc" is inconsistently used).
plˈænd tˈɛsts ɑːɹ dɪtˈɜːmɪnd bᵻfˌoːɹ lˈʊkɪŋ æt ðə dˈeɪɾə, ænd pˈoʊst hˈɑːk tˈɛsts ɑːɹ kənsˈiːvd ˈoʊnli ˈæftɚ lˈʊkɪŋ æt ðə dˈeɪɾə ðˌoʊ ðə tˈɜːm "pˈoʊst hˈɑːk" ɪz ɪŋkənsˈɪstəntli jˈuːzd.