Geometrically it is the slope of the line intersecting a certain point of a curve or a function
Like this:
Meaningfully, it is the rate at which the output variable (y) of a function changes in an instant. For example:
if y = x^2
from x = 0 to x2 = 2
the value of y changed by ((2^2) - (0^2))/2 = 2
so the rate of change between 0 and 2 is 4
the derivative is a way of getting a rate of change at an exact instant(or a single point) with no time interval
so let's say: x = 2 and now the second x is getting closer and closer to 2
so
x=2 x2=2.1000
x=2 x2=2.0100
x=2 x2=2.0001
if you do this forever the value between x and x2 get infinitely small so we can ignore it completely.
then if you calculate the rate of change between the two points x=2 and x2=2.0001 you get
(2.0001^2 - 2^2)/0.0001
which is approximately equal to 4, which is the slope of the line tangent to the point (2,4) on the graph y=x^2
if you have any questions, leave me a response, I typed this in like 5 minutes lol