Hizb 1 is the only one of the sixty that begins at the true start of the Quran rather than partway through a surah already in progress, since it opens with Al-Fatiha itself. Everywhere else, a hizb boundary falls wherever the running length reaches its mark, which is exactly what happens at the other end of this one: it stops in the middle of Al-Baqara's address to the Children of Israel, with no regard for where that argument would naturally pause.
Like every hizb, this one is further marked in a printed Mushaf's margin into four rub al-hizb quarters, finer graduations than the medallion that marks the juz itself, meant to let a reciter or a memoriser gauge progress within a single sitting rather than only across a whole night. The sixty-part scheme runs alongside an older sevenfold division called the manazil, used by those who complete the whole Quran across a week rather than a lunar month, though the hizb and quarter marks belong to the thirty-juz monthly scheme rather than to that weekly one.
Paired with Hizb 2, this hizb makes up Juz 1, the portion most commonly recited on the first night of tarawih prayer during Ramadan in communities that pace the month one juz per night. Huffaz reviewing memorised material often use the two ahzab of a juz, and the four quarters within each, as a steadier unit for daily review than the surah boundaries themselves provide, since Al-Baqara alone runs across five juz and gives no natural stopping point of its own.