Google Instant is a new search feature launched by Google that displays predictive search results as a user types their query, without needing to press enter. It has the potential to significantly impact search engine marketing and optimization. Some of the key ways it could affect SEM and SEO include changes in user search behavior, a potential shift in traffic from long-tail to more general keywords, and increased importance of keyword expansions and keywords displayed in Google's suggestions. Its overall impact on advertisers and SEOs remains unclear and will need to be closely monitored.