The phrase "new window" refers to opening a separate and independent page or tab on a computer screen that allows you to view different content without closing the current one. Full definition
(Opens in new window) The baby was placed in the nest beside me in my bed. (easybabylife.com)
Be aware though, that not all pop - ups are bad - some sites open new windows in this way. (moneysavingexpert.com)
She tells owners who want to cut energy bills to start with insulation — likely a third of the cost of new windows — or just get a smart thermostat. (realtormag.realtor.org)