If you mean meta title tag, than it is used in <head> </head> of your web page source. Title tag is very important and search engines / Google considers this tag while evaluating sites for ranking. It is suggested to use website keyword; relevant to page content in title tag for improved ranking. Besides, web page title is the first thing showed in SERPs. ALT tag is used with images and it is also another tag where we can use keywords. But our intention should not be to use only keywords, instead this tag is basically used to define the image. For example, if you have a picture of your school baseball team, than you can write ALT tag like, "School Baseball Team 1998" and likewise. Hope this helps.
I agree.. See the title of this page at top of your browser. This is also shown in search result and SE value it most. ALT tag is used for image. When due to some reason like slow connection or browser setting Image do not load and then "alt" is visible and a visitor can know what was there. if you check the property of any image ( by right click) it will show the associated alt text with image.
I think this guy was talking about the title="" tag you find on links. This tag is very similar to the ALT tag on an image in a sense that it is used to tell screen readers what the link says, so it can read them out. It's an accessibility tool. I'm not sure if it offers any SEO benefit. If you believe in the keyword density theory, then it probably does.