When we talk about "improving performance" we're referring to things like greater throughput, more concurrent users served, improved responsiveness. Putting aside blue pills and nasal delivery systems, scaling application development is after much the same thing. When it comes to web applications, delivering your message as fast as you can leads to greater user satisfaction.
Last year the MMORPG, Eve Online, released a patch that had the potential to bugger the operating system install of any Windows user upgrading. This monumental blunder bypassed engineering and QA processes to end up in the hands of tens of thousands of unwitting consumers.