If you wanted to get it down to the nutshell of what Video Alchemy does its founder Michael Sime would say "We make monitors work so you can shoot them with a film camera".
A bit more detail would include:
Visual Alchemy provides complete video and computer services to the film production industry. They operate true 24 frame synch video/computer feeds & displays with film-video synchronization, with the best operators around. In addition to their on-set playback services, Visual Alchemy also offers full-service content creation, including video acquisition (shooting) & editing (on-set or off), computer graphic and animation design, video projection, and set dressing/prop rentals. Their crews include video engineers, shooters, editors, graphic artists & animators, all well versed not just as editors/shooters/etc, but specifically, in using those talents to create content as playback elements.