The DIM command is used to create an array. an array is simply a set of variables. For example try:
DIM A[10]
FOR I=0 TO 9
A[I]=RND(100)
NEXT
SORT A
FOR I=0 TO 9
?A[I]
NEXT
END
This should create a random set of numbers, sort them, and finally display them.
In SmileBASIC, DIM is the exact same as VAR in every way, in other versions of the BASIC programming language, DIM is how you create an array, so by convention we use DIM only for arrays
But it's up to you
DIM A$[5]
A$[0]="1st item"
A$[1]="2nd item"
A$[2]="3rd item"
A$[3]="4th item"
A$[4]="5th item"
Then if you ever want to know what you had inside the third array item
PRINT A$[2] 'print 3rd Item