This is something like GlideModal or GlideWindow. It expects a object as
part of its call;

var theObject = {
    id    : 'test-id',//seems to be the ui page it uses
    title : '',//self explanatory
    width : '',//self explanatory
    height: '',//self explanatory
    draggable: true,
    form: 'incident',
    iframe: '',
    onAfterLoad: null,//expects a function, see UI Script "KBViewArticle" for example
    onAfterClose: null,//expecs a function, see ui action "Add" on cmdb_outage_ci_mtom
    closeOnEscape: true,
    showClose: true,
    messages: "",
    allowOverFlowX: true,
var go = new GlideOverlay(theObject);
// you can also set things...
go.setPreference('sysparm_error','error msg');
go.setAfterLoad(null);//expects function
go.setTitle('the new title');;
// I found these by running this in console
// on my browser
// var a = new GlideOverlay({});
// for(var p in a){
//   if(typeof a[p] === 'function'){
//    console.log('go.' + p + '();');
//   }
// }

// GlideOverlay.close('test-id');
// window.parent.GlideOverlay.close('test-id');
Property/Method Description
_escapeCloseHandler Unknown
_focusHandler Unknown
initialize Unknown
isModal Unknown
closeOnEscape Unknown
close Unknown
toString Unknown
constructor Unknown
getId Unknown
getBoxElement Unknown
getBoxWrapperElement Unknown
getIFrameElement Unknown
isVisible Unknown
isLoading Unknown
setOnClick Unknown
setOnBeforeLoad Unknown
setOnAfterLoad Unknown
setOnBeforeClose Unknown
setOnAfterClose Unknown
setOnBeforeDrag Unknown
setOnAfterDrag Unknown
setOnBeforeResize Unknown
setOnAfterResizes Unknown
setOnHeightAdjust Unknown
setOnWidthAdjust Unknown
addData Unknown
getData Unknown
getToolbar Unknown
addToolbarRow Unknown
setTitle Unknown
setTitleHtml Unknown
setWindowIcon Unknown
addWindowIcon Unknown
removeToolbarDecoration Unknown
addToolbarLeftDecoration Unknown
addToolbarRightDecoration Unknown
addToolbarCloseButton Unknown
removeToolbarCloseButton Unknown
setToolbarCloseOnClick Unknown
_addToolbarDecoration Unknown
getFooter Unknown
showFooter Unknown
hideFooter Unknown
showFooterResizeGrips Unknown
hideFooterResizeGrips Unknown
getFooterContainer Unknown
setFooter Unknown
prependFooterRow Unknown
appendFooterRow Unknown
_addFooterRow Unknown
getMaxDimensions Unknown
getDocumentHeight Unknown
getDocumentWidth Unknown
autoDimension Unknown
size Unknown
setMaxWidth Unknown
setWidth Unknown
setMinWidth Unknown
setHeight Unknown
setMinHeight Unknown
getMaxPositions Unknown
autoPosition Unknown
center Unknown
setMaxTop Unknown
setMinBottom Unknown
positionTop Unknown
positionLeft Unknown
positionRight Unknown
positionBottom Unknown
convertToLeftPosition Unknown
convertToRightPosition Unknown
setStyle Unknown
getWidth Unknown
getHeight Unknown
getStyle Unknown
getOffset Unknown
getBodyElement Unknown
getBodyWrapperElement Unknown
setBody Unknown
setBodyFromForm Unknown
setBodyPadding Unknown
_getViewportDimensions Unknown
setDraggable Unknown asdfasdfasdfasdfasdfasdfsad
isDraggable Unknown
setPreferences Unknown
setPreference Unknown
getPreferences Unknown
removePreference Unknown
getDescribingXML Unknown
getDescribingText Unknown
hide Unknown
show Unknown
render Unknown
_renderStatic Unknown
_renderForm Unknown
_renderIFrame Unknown
_createIframeShim Unknown
_resizeIframeShim Unknown
_removeIFrameShim Unknown
_isQuirksMode Unknown
_focusHandlerPrototype Unknown
_activateFocusTrap Unknown
_deactivateFocusTrap Unknown

IFrame example

var o = new GlideOverlay({
    title : "Edit Metadata Request",
    iframe : metadataservice_gui_url,
    allowOverflowX : true,
    height : 650,
    width : 1000
    //messages : ""

UI Page example

new GlideOverlay({
  title: new GwtMessage().getMessage('Run Fix Script'),
  form: 'run_fix_script_dialog',
  preferences: {
  'sysparm_script_name': gr.u_notes,
  'sysparm_sys_id': gr.sys_id
  width: 600

Further Reading: