The Prophet Muhammad SAW taught that when a person dies, their deeds come to an end except for three things.
1. Ongoing Charity Sadaqah Jariyah
Charity that continues to benefit others, such as supporting a mosque, school, water supply or other lasting community benefit.
2. Beneficial Knowledge
Knowledge that was taught, written or shared and continues to benefit others after one's death.
3. A Righteous Child Who Prays for the Parent
A righteous son or daughter who continues to make dua for their deceased parents.
Source of Hadith
Narrated by Abu Hurairah RA.
Sahih Muslim
Book of Wills
Hadith 1631
The meaning is that these three can continue bringing reward to a person even after death.