Phone virus kinda

(I don't have pictures now bc when I restarted the phone it stopped) On my mom's old phone popups started showing up with "your phone is overheating click here to cool it down" or "you're out of storage click here to save some" I would say it's a phone cleaner but it had ads which most don't (aside from avast) have idk if it just tricks you into watching an ad or if it's serious