Reserving the size of vector

#1

sir in the video, sir has told about reserve function of vector.
i want to know is there any difference in these two methods of declaring size of vector ?
1 .) vector v;
v.reserve(1000); and
2.) vector v(1000) ;

#2

void reserve (size_type n);

Request a change in capacity

Requests that the vector capacity be at least enough to contain n elements.

If n is greater than the current vector capacity, the function causes the container to reallocate its storage increasing its capacity to n (or greater).

but this is not the case in v(1000)

#3

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