My own understanding is that "intellectual assets" is just a fancy name for what used to be loosely termed intellectual property (e.g. copyrights, patents, trade secrets (specialist know-how) but has been extended to include items such as trademarks and brands.
Such assets are considered intangible or hidden but their value is figuring much more in modern day mergers and acquisitions. Indeed, some leading consultancies will to attempt to assign value to such assets. The "management" of these assets is identifying how to derive best value from them.
Hope this helps