The expression E1 to E2 returns a sequence of integers. For example, 1 to 5 returns the sequence 1, 2, 3, 4, 5. This is useful in for expressions, for example the first five nodes of a node sequence can be processed by writing for $i in 1 to 5 return (//x) $i. Another example:
(1+1 to 10)
result:
xs:integer: 2
xs:integer: 3
xs:integer: 4
xs:integer: 5
xs:integer: 6
xs:integer: 7
xs:integer: 8
xs:integer: 9
xs:integer: 10