A lower pH means a higher acidity, and thus a higher concentration of positive hydrogen ions in the solution.
ɐ lˈoʊɚ pˈiː ˈeɪtʃ mˈiːnz ɐ hˈaɪɚɹ æsˈɪdᵻɾi, ænd ðˈʌs ɐ hˈaɪɚ kˌɑːnsəntɹˈeɪʃən ʌv pˈɑːzᵻtˌɪv hˈaɪdɹədʒən ˈaɪɑːnz ɪnðə səlˈuːʃən.