The collect (or collecting) construct takes one form in its clause and adds the value of that form to the end of a list of values. By default, the list of values is returned when the loop finishes.
The append (or appending) construct takes one form in its clause and appends the value of that form to the end of a list of values. By default, the list of values is returned when the loop finishes.
The nconc (or nconcing) construct is similar to the append construct, but its list values are concatenated as if by the function nconc. By default, the list of values is returned when the loop finishes.
The sum (or summing) construct takes one form in its clause that must evaluate to a number and accumulates the sum of all these numbers. By default, the cumulative sum is returned when the loop finishes.
The count (or counting) construct takes one form in its clause and counts the number of times that the form evaluates to true. By default, the count is returned when the loop finishes.
The minimize (or minimizing) construct takes one form in its clause and determines the minimum value obtained by evaluating that form. By default, the minimum value is returned when the loop finishes.
The maximize (or maximizing) construct takes one form in its clause and determines the maximum value obtained by evaluating that form. By default, the maximum value is returned when the loop finishes.
For more information, see Section 6.1.3 (Value Accumulation Clauses).