"Shared memory" means a video adapter takes system RAM to use for video memory. As for games, it's ok for watching movies and low-end/older games like Counter-Strike, Starcraft, The Sims etc. but not stuff like Oblivion & Crysis.
See the list of laptop graphics adapters below, the best ones are listed first.
Intel's GMA 4500MHD ranks class 3, around 2/3 of the way down the page. It's part of the lower-middle class of mobile graphics adapters.