Flash can be used to put together all types of interactive projects, from complete web sites to animated advertisements and everything in-between.
While the introduction of the HTML 5 specification is reducing (and will eventually eliminate) the need for some of its more basic applications (such as embedded video players), Flash still serves a large number of uses that simply can't be recreated with markup alone.
Games:

Developing online, browser-based games is where Flash really shines. Just about any type can be developed then delivered seamlessly through all major browsers; Internet Explorer, Firefox, Chrome, Opera and more.
While entertainment orientated sites are likely familiar with the appeal already, promotional games are an excellent way to attract more visitors to all kinds of sites and keep them on there for longer. In addition to their entertainment value, they can also be used to train and educate visitors where it relates to the product or service you're offering.
Interactive Presentations:

In the age of Youtube, it's become popular to create videos to showcase all types of things, but video remains a one-way medium for presentations. Utilizing Flash (which can include full video as well), users are able to interact with what they're being shown; having the presentation change or customize based on their input in any number of ways.
Depending on how it's built, Flash presentations normally offer some significant bandwidth savings over using video exclusively as well, making for faster load times.
Complete Web Sites:

While it's often not the best idea, there are certain times in which flash-based web sites makes good sense. The additional interactivity, animation and the ability to include sound throughout can make for very compelling presentations when compared to traditional HTML based sites.
It normally takes significantly more time to make content changes on Flash sites than their counterparts, so they're more conducive to making intriguing sites that won't be changed or added to often. Entertainment portals, realty showcases, and game-based sites are just a few examples of all-flash sites we've developed for clients that worked well for their intended audience.
Animated/Interactive Advertisements

Flash ads continue to be widely used when possible, allowing for "hot spots", rollover information, and other features unavailable with simple images. We've been making interactive ads for well over a decade, creating eye-catching designs for banners and interstitials that comply with today's media standards, maximizing CTR's and improving your ROI on advertising buys.