Flash is a powerful authoring tool that can help you create games from the simple to the extremely complex.
Flash's strengths and limitations make it ideal for creating some kinds of games and less than optimal for others.
ActionScript the programming language used in Flash is going to be the main tool through which you bring your games to fruition.
Familiarizing yourself with game genres and terminology is a good first step toward deciding what sorts, and levels, of games interest you as a developer and will also show you where you need to brush up!
For reasons of portability, extensibility, integration, file size, and near-universal access, Flash is a good choice for games you'd like to make available on the Internet.
Flash is easy enough to learn that you can be up and creating games in a very short time.
A high cost of the small file sizes and accessibility of Flash games is their slow performance relative to games created on virtually all other game-development platforms.