An array is a collection of similar variables in which each has the same name and they all have they same type . The first element in an array usually has an index value of 0 . An array can be  different sizes.

Here is the syntax of an array.

Dim | Public | Private ArrayName (subscript ) As DataType

Dim | Public | Private are the keywords which declare an array and its scope . If you use Dim the array i sprivate to the procedure in which its declared . Public makes the array visible anywhere in the program and Private makes the array visible only to the form or module in which its declared . I usually declare an array in the General Declarations section with Dim and this means the array is available to all procedures within the module.

ArrayName is the name that you use for the array.

( subscript ) is the highest number of the array.

As is the Visual Basic keyword that signifies a type declaration

DataType is a valid Visual Basic type , such as Integer

If you set Option Base 1 in the General declarations section of a module then the first element of the array would be 1 but by default the first element of an array is 0.

Example

Dim intMyArray(2) As Integer

intMyArray(0) = 24
intMyArray(1) = 58
intMyArray(2) = 7

This declares an array of 3 elements of type integer and then assigns a value to them.

You can also declare an array using the To keyword , this is a convenient way of setting your starting element at a number other than 0 like this.

Dim intMyArray (1 To 10) As Integer

Changing the number of elements

To change the number of elements in an array you have to redimension it using the ReDim keyword , here is the syntax.

ReDim [Preserve] ArrayName( subscript ) As dataType

ReDim is the keyword for redimensioning
Preserve is optional and this forces all existing elements in an array to hold their values . If this is omitted all values in the elements is lost and each element is changed to zero for numerics and "" (zero length string) for strings.
ArrayName is the name of the array
subscript is the highest value of the array
As is the keyword that signifies a type declaration
datatype is the valid Visual Basic Type , Integer or Single for instance

Here is an example that redimensions our first array

ReDim Preserve intMyArray(6) As Integer