Refers to traditional Japanese festivals marking seasonal turning points, such as 五節句 (the five seasonal festivals).
端午の節句には鯉のぼりを飾ります。
We display carp streamers for the Boys' Festival.
桃の節句は女の子の成長を祝う日です。
The Dolls' Festival is a day to celebrate the growth of girls.
The whole family celebrated the Girls' Festival together.
There's a custom of eating chimaki on the Boys' Festival.