What does “chain” attribute in Arduino programming mean? And how to implement it? We are using wokwi as our online Ardui

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What does “chain” attribute in Arduino
programming mean? And how to implement it? We are using wokwi
as our online Arduino Simulator, so please can you explain using
wokwi libraries?
Here is 2 examples of questions :
1. Connect LED Matrix with “chain” attribute is 1 and 4 buttons
with suitable resistors to Arduino Mega. Write a code to control a
dot/LED move up, down, left, and right using 4 buttons. At the
beginning, the dot location will be (0,0). Only one dot/LED is
displayed at once and this dot/LED can only display within the 8x8
range.
2. Connect DS1307 RTC and LED Matrix with “chain” attribute is 5
to Arduino Mega. Write a code to display the current time from
DS1307 RTC to LED Matrix with the speed value is 10, pause value is
100, and text alignment is PA_CENTER.