"Organic traffic" is traffic that comes to your website as a result of unpaid search results. Frequently, one of the goals of SEO is to increase organic traffic.
The service is basically used after having some updates on website so that the bots visit the webpage to check the updates and get them added to their data. But as bots are getting too clever and sharp, it is better to not to use such services anymore.
The term "ALT tag" is a common shorthand term used to refer to the ALT attribute within in the IMG tag. Any time you use an image, be sure to include an ALT tag or ALT text within the IMG tag. Doing so will provide a clear text alternative of the image for screen reader users.