What is personality in this request?

Trying to create (run) an instance via OS API, here is the request body:

{
    "server" : {
        "name" : "new-server-test",
        "imageRef" : "http://servers.api.openstack.org/1234/images/52415800-8b69-11e0-9b19-734f6f006e54",
        "flavorRef" : "52415800-8b69-11e0-9b19-734f1195ff37",
        "metadata" : {
            "My Server Name" : "Apache1"
        },
        "personality" : [
            {
                "path" : "/etc/banner.txt",
                "contents" : "ICAgICAgDQoiQSBjbG91ZCBkb2VzIG5vdCBrbm93IHdoeSBp dCBtb3ZlcyBpbiBqdXN0IHN1Y2ggYSBkaXJlY3Rpb24gYW5k IGF0IHN1Y2ggYSBzcGVlZC4uLkl0IGZlZWxzIGFuIGltcHVs c2lvbi4uLnRoaXMgaXMgdGhlIHBsYWNlIHRvIGdvIG5vdy4g QnV0IHRoZSBza3kga25vd3MgdGhlIHJlYXNvbnMgYW5kIHRo ZSBwYXR0ZXJucyBiZWhpbmQgYWxsIGNsb3VkcywgYW5kIHlv dSB3aWxsIGtub3csIHRvbywgd2hlbiB5b3UgbGlmdCB5b3Vy c2VsZiBoaWdoIGVub3VnaCB0byBzZWUgYmV5b25kIGhvcml6 b25zLiINCg0KLVJpY2hhcmQgQmFjaA=="
            }
        ]
    }
}

What is personality? Is that a keypair file, or what?