Alt text stands for ‘alternate text’. It describes what is depicted on the image. This is an attribute of an HTML image tag. If the image can’t be displayed for no matter what reason, the alt text will be shown instead. Alt text also helps searche engines to understand what is there on the picture.
Image title is shown is a small pop-up box when you place tour cursor on the image. Title and Alt text are usually different. But they both improve your website accessibility for those who have to use a screen reader device.
If we speak about SEO, the alt text is more important for it, so don’t ignore it.