From Facebook Developer Wiki

These are the parameter types that are used in API calls and FBML tags. These are all normally sent as "strings" anyway, but allow you to know what kind of data to put for the parameter. See json.org for details on JSON syntax.

Contents 1 array 2 bool 3 data 4 float 5 int 6 markup 7 object 8 string 9 time

array

An ordered collection of JSON-encoded values. For example, ['val1','val2','val3']

Note: Any API method in production before 10 February, 2009, can also take comma separated values in the array.

bool

A boolean, specified as true or false, yes or no, or number≠0 or 0.

data

Raw data. Currently used in the photos.upload API method to transmit the raw image data of the photo being uploaded.

float

A float. Currently used for specifying the weight of an fb:random-option, the version number in fb:fbml, and for the coordinates of a photo tag in the photo_tag FQL table.

int

An integer. Usually used for IDs of various types. Unless otherwise noted, ints have 64-bits of precision.

markup

FBML markup.

object

An object containing an unordered collection of JSON-encoded name/value pairs. For example, {'val1': 1, 'val2': 2, 'val3': 3}

string

A string of text.

time

An integer representing the number of seconds since January 1, 1970 (UTC). Commonly known as "unix time."