You're much better off to use two and three word combinations than single keywords. That's what search engine users tend to type in order to get more targeted results. Many people overlook the title tag as unimportant, but the truth is search engines do look at it and weigh it when ranking your site. Again, try to repeat them two or three times if you can do so without compromising the description. Remember that the length of the description tag is best kept at under 25 words.
Alt tags are where web designers write a short description of pictures used on the pages.
This is done as a convenience for those who surf the Web with graphics turned off.