yes Redim can be used to declare a new array.

No We can't use redim to declare a new array. Redim is used 
to resize the declared array

M. chitramala is right. Redim is to resize the exiting 
array variable.

sample:
Dim myarray() as string

Redim myarray(10)

Redim is used to increase the dimension/size of the array.  
Preserve keyword is used to hold the previous value of the 
array.

ex:  Redim Preserve a[20]

redim can only be used to increase/decrease the size of the 
existing array.it cannot be used to create a new array.

srinivas  shetty

yes friends its right redim is used to resize the decalred
array realier in the program

if I redim an array and increase its size. will the 
existing elements in the array be lost?

Yes, Using Redim statement the size is set at runtime.