What is a narrative beat? can anyone give me an example of it? i'm stuck with with my assignment which requires me to give a narrative beat

Depending on who you talk to, a narrative beat is similar to a plot point, just a moment in your story that moves the plot along. Sometimes they are big, like when Uncle Ben dies in "Spiderman" or small when we find out the Gil, in "Finding Nemo", has tried to escape from the fish tank.

Generally there are three major "narrative beats" or "plot points" in a basic 3 act structured screenplay. Each one exists before the next act to help propel the story into the next act and add momentum to the story (they usually put more stress on the main plot of the story and / or put your protagonists in more dire situations).

The farm boy who wishes for something better, who knows he has
something more to offer is given that opportunity.

“I need your help Luke. She needs your help. I’m getting to old
for this sort of thing”

“I can’t get involved. I’ve got work to do. It’s not that I like
the Empire - I hate it. But there’s nothing I can to about it
right now. It’s such a long way from here”

“That’s your Uncle talking.”

But then when his Aunt and Uncle are killed by the very Empire he
hates, the narrative beat or plot point happens:

“I want to come with you to Allderon. There’s nothing for me
here now. I want to learn the ways of the force and become a Jedi
like my father.”