This is the 8699th most frequent Russian word.
пасху
"Пасху" is the accusative form of "Пасха," meaning "Easter" in English.
In this sentence, "Пасху" refers to the holiday Easter, being in the accusative case as the object of the preposition "на" indicating motion.
На Пасху мы каждый год красим яйца.
On Easter, we dye eggs every year.
Here, "пасху" is implied in the context of the time, not used directly but its adjective, indicating being for or relating to the Easter holiday.
Мама испекла куличи к Пасхе.
Mom baked Easter cakes for Easter.
"Пасху" in this sentence is marking the holiday in a temporal sense, showing the time during which the action occurred.