What is wp_commentmeta used for? Can I Empty the Table from MySQL

Can any one here explain me what is the use of “wp_commentmeta” table in mysql.

In my database, the table is taking 4 – 5 mb space, if data in this table is not required, is it safe to empty the table from mysql?

When i browse table, I can see all spam or junk links caught by Akismet.

Let me know.