In modern television advertising parlance, Integration is both the act of including product placements in television shows and how effectively that inclusion is handled.
Product integration is a tricky thing to do right - on the one hand, a company wants their brand to be included in a program in such a way as to be noticable to the viewer, but on the other they shouldn't be so incredibly obvious as to lower the viewer's opinion of the brand. In other words, a police car manufactured by Ford is a perfectly reasonable occurrance in your typical Friday night cop show, but a ten-second vanity shot of the Ford logo that brings the plot to a standstill for its duration is a waste of time and money - viewers would remember the brand, sure enough, but their opinion of it would be substantially lowered.
It should be noted that the term Integration doesn't apply to product occurrences outside the normal world of the programming - an on-screen graphic inviting viewers to download episodes of a show from iTunes doesn't fall under integration, but a character saying that she downloaded a kickass song from iTunes does.