Depending on the "type" value the function returns:

"address" : the specified reference as text

"col" : column number of the specified cell

"row" : row number of the specified cell

"color" : 1 if the current cell format is set to display negative numbers in red; 0 otherwise

"contents" : value of the specified cell

"filepath" : filename and full path of current document

"format" : symbol of the format code of the specified cell, as listed below

"parentheses" : 1 if the current cell format is set to display negative numbers in parentheses; 0 otherwise

"prefix" : single quotation mark (') if the cell contents is left-aligned, double quotation mark (") if the cell contents is right-aligned, caret (^) if the cell contents is centered, empty text in all other cases

"protect" : 1 if the specified cell is protected

"type" : "b" if the cell is empty, "l" if the cell contains text, "v" in all other cases

"width" : number of characters in the default font size fitting in the specified column

General    "G"
0    "F0"
#,##0    ",0"
0.00    "F2"
#,##0.00    ",2"
$#,##0_);($#,##0)    "C0"
$#,##0_);[Red]($#,##0)    "C0-"
$#,##0.00_);($#,##0.00)    "C2"
$#,##0.00_);[Red]($#,##0.00)    "C2-"
0%    "P0"
0.00%    "P2"
0.00E+00    "S2"
# ?/? or # ??/??    "G"
m/d/yy or m/d/yy h:mm or mm/dd/yy    "D4"
d-mmm-yy or dd-mmm-yy    "D1"
d-mmm or dd-mmm    "D2"
mmm-yy    "D3"
mm/dd    "D5"
h:mm AM/PM    "D7"
h:mm:ss AM/PM    "D6"
h:mm    "D9"
h:mm:ss    "D8"

=cell("address", sheet1!$a$2) returns "sheet1!$A$2"

=cell("address", sheet1!a2) returns "sheet1!A2"

=cell("width", b10) returns 9

Counts empty cells and cells containing empty strings for the specified list of arguments.

=countBlank({1, 2, 3,,}, {""},,) returns 5

Returns an integer representing a given error value.

For the complete list of error codes, please see the 'Data types' help topic.

Returns 1 if 'x' refers to an empty cell or an empty string, 0 otherwise.

=isBlank("") returns 1

Returns 1 if 'x' is an error value except #N/A!, 0 otherwise.

=isErr(1/0) returns 1
=isErr(#SYNTAX!) returns 1

Returns 1 if 'x' is an error value, 0 otherwise.

=isError(#N/A!) returns 1

Returns 1 if 'n' is even, 0 otherwise. All numbers are rounded to the nearest integers.

=isEven(12) returns 1

=isEven(12.6) returns 0

Returns 1 if 'n' is 1 or 0, 0 otherwise.

=isLogical(1) returns 1

Returns 1 if 'error' refers to the #N/A value, 0 otherwise.

=isNA(#N/A!) returns 1

Returns 1 if 'x' refers to any value that is not a text string, 0 otherwise.

=isNonText("") returns 0
=isNonText(1) returns 1

Returns 1 if 'x' represents a number (which also includes a string that can be converted to a number), 0 otherwise.

=isNumber(9) returns 1
=isNumber("9") returns 1

Returns 1 if 'n' is odd, 0 otherwise. All numbers are rounded to the nearest integers.

=isOdd(12) returns 0

=isOdd(12.6) returns 1

Returns 1 if 'x' is a reference, 0 otherwise.

=isRef(a1) returns 1
=isRef({1,2,3}) returns 0

Returns 1 if 'x' represents a text string, 0 otherwise.

=isText("a") returns 1

Converts x to a number.

=n("2005") returns 2005

Returns the #N/A error value.

=na() returns #N/A!

Returns the type of x:
1 Number
2 Text
16 Error value
64 Array

=type(1) returns 1

=type({1, 2, 3}) returns 64