Inkscape creates SVG (Scalable Vector Graphics) files. SVG images have the advantage of displaying at any size without error or distortion. You can use the SVG files in modern Web browsers and export them to JPEG and other formats for use in old Web browsers.
You can get a portable version for use in Windows based computers from a USB flash memory devices, also known as USB drives, USB pen drives, and a dozen other names. Download from www.winpenpack.com/en/download.php?view.40. You do not need a portable version because Inkscape is free from cost and free from licensing restrictions. You can freely download it to every computer you work on, install it, and leave it there for the next user.
What can you do with Inkscape? Visit openclipart.org to view examples. You will see all sorts of 2D graphics. SVG handles 3D graphics and Inkscape has not tackled 3D graphics. Photographs and other raster images are best edited with Gimp. You can use raster images from Gimp as backgrounds in SVG elements then move the elements around within an SVG image.
Inkscape is an open source alternative to Illustrator (US$599), CorelDraw (US$489.00), and Xara X (US $249).
How does Inkscape compare to Illustrator and CorelDraw? Illustrator and CorelDraw fans argue over which is best. CorelDraw was the first big drawing application and Illustrator is backed by Adobe, the 900 pound gorilla of the illustration market. Both CorelDraw and Illustrator are aimed at drawing without regard to the output format. Inkscape is focused on SVG. If you work mostly in other formats, look at the other tools. You can download and trial Inkscape forever with no restriction before spending the big bucks on those other products.
How does Inkscape compare with Xara X? Xara have a bunch of products and the top of the line appears to combine the functions of Gimp, Inkscape, plus HTML editors. The Xara Pro product looks a bit like Microsoft Works and some other products that attempt to do everything. Xara Pro has HD (High Density) Photo Import but no option to plug in the industry standard Photomatix. When someone asks you for a professional print from one of your HDI files, you will need Photomatix or equivalent. You will end up with Adobe Photoshop to edit your images then the Adobe range of products will look more interesting that Xara. Overall Xara looks more like a tool for assembling things as posters and brochures. You create the things with other more focused tools. The HTML features are not needed when you use a good content management system.
Inkscape is free to try as long as you like. Try Inkscape first. Work through the many tutorials scattered over the Web. If there is something specific you need that is not in Inkscape or in Gimp, download a trial of either CorelDraw or illustrator or Xara.
PS, when you find a really good tutorial, mention it in a comment here with link to your finished illustration based on the tutorial.