Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, Freehand, CorelDraw, or Xara X using the W3C standard Scalable Vector Graphics (SVG) file format. Supported SVG features include shapes, paths, text, markers, clones, alpha blending, transforms, gradients, patterns, and grouping. Inkscape also supports Creative Commons meta-data, node editing, layers, complex path operations, bitmap tracing, text-on-path, flowed text, direct XML editing, and more.
It imports formats such as JPEG, PNG, TIFF, and others and exports PNG as well as multiple vector-based formats. Inkscape's main goal is to create a powerful and convenient drawing tool fully compliant with XML, SVG, and CSS standards. We also aim to maintain a thriving user and developer community by using open, community-oriented development process, and by making sure Inkcape is easy to learn, to use, and to extend. While Inkscape does not have all the features of the market leading proprietary software, the latest versions provide for a large portion of basic vector graphics editing capabilities.
People report successfully using Inkscape in a lot of very different projects (web graphics, technical diagrams, icons, creative art, logos, maps). See examples at the Galleries. We try to always keep the codebase usable for real users, as we believe that a tight iteration cycle between users and developers will give best results. You can start using Inkscape alongside your other tools now!

Other Features
Why is Inkscape so different from Adobe Illustrator? In many cases, this is simply because the feature in questions is not yet implemented, or is being actively worked on right now. But there are other reasons, too. AI is not the only game in town. Even though it currently enjoys a near-monopoly position, there still exist, for example, CorelDraw and Xara - which are also quite different and, in the opinion of many people, superior to AI in usability. Inkscape has borrowed a lot of user interface ideas from these fine editors. We take usability very seriously, and we often knowingly depart from the AI paradigms because we consider our approaches better.
Is Inkscape a replacement for The GIMP or Photoshop? In most cases, no. They're used for two very different things. Inkscape is used for creating vector drawings, such as laying out a poster or creating a fancy logo, whereas bitmap editors are for working on raster images, such as touching up a photograph. In many projects, you would need to use both Inkscape and a bitmap editor (such as GIMP), for example, to add bitmap effects to an image exported from Inkscape.