The <caption> tag defines a table caption. It must be inserted immediately after the <table> tag. One caption per table.
The text in a caption element gets more emphasis then other words, it is usually centered.
The caption text says something about the data in the table below it. It could be seen as the 'parent' of the items in the table.
It is very possible this tag gets special consideration in Google's and other search engine algorithms. Consider the following questions:
In the HTML example above, which word would you deem more important, laptops or Xl72V ?
Do you think this HTML snippet should rank for Xl72V Laptops ?