How to use get the Offfset X and Y value of a webelement from a web page. Please explain in steps

Explain the steps to get the Offset X and Y value of a webelement from a web page.Does the value of these remain constant throughout or may change ;in what circumstances?

Do you mean the X and Y in, as an example, the statement below:

WebUI.clickOffset(findTestObject('myPage/canvas_tic-tac-toe-board'), X, Y)