In basic terms, the apex or clipping point is the point on the inside portion of a corner that a vehicle passes closest to.
ɪn bˈeɪsɪk tˈɜːmz, ðɪ ˈeɪpɛks ɔːɹ klˈɪpɪŋ pˈɔɪnt ɪz ðə pˈɔɪnt ɔnðɪ ɪnsˈaɪd pˈoːɹʃən əvə kˈɔːɹnɚ ðˌæɾə vˈiəkəl pˈæsᵻz klˈoʊsɪst tuː.