mainly Select-options is used for selection screen..
where as ranges is used inside the program..

Ranges cannot visible in selection screen

Functionality wise there is no difference except SELECT-
OPTIONS are visible in the selection screen while Ranges 
are not visible.

Both have same structure. 

One restriction in Ranges is u can't use Range in Select 
query if it has more than 2000 entries.

Ranges are used just like we use temporary internal tables.
eg: If u want to check for say 10 ranges in select query 
for some field which is not there in ur selection screen 
then u will populate the ranges and use it in the select 
query. Syntax will remain same as select option.

RANGES: r_vbeln FOR vbak-vbeln.

r_range-sign = 'I'.
r_range-option = 'BT'.
r_range-low = 123.
r_range-high = 321.
APPEND r_range.

like this append all the ranges u want.

SELECT field list FROm vbak INTO TABLE i_vbak
WHERE vbeln IN r_vbeln.