Question

what do you mean by acceleration?

Answer 1

acceleration is the rate of change velocity at the time
a=v-u/t and is a vector quantity

Answer 2

here's your answer looking for

Acceleration :- acceleration is rate of change of velocity.
it determines at what rate the velocity is changing.

it's also a vector quantity,

mathematically we can represent it by the following expression:-

$a = \frac{ {v}^{2} - {u}^{2} }{t}$
it's SI unit is
$m {s}^{ - 2}$
hope you are satisfied with my answer