What does the keyword `capturing` do?

I noticed that the keyword

capturing

capturing

is necessary when I want to time code via

time_function

time_function

. For example,

from time import time_function

fn closure() capturing:
    my_function()

print(time_function[closure]() * 1e-9)

from time import time_function

fn closure() capturing:
    my_function()

print(time_function[closure]() * 1e-9)

What is going on under the hood if I am using the keyword

capturing

capturing

? I have not found documentation on this.