Don't get Gimp and Inkscape confused. Gimp works with bitmaps and inkscape works with vectors. If you don't understand the difference, don't feel bad, a lot of people don't. Think of a bitmap as a grid of squares drawn on paper, you fill in each square wit a color. That's why some graphics have jaggy edges. Bitmaps are like what you get from a camera or scanner. Like a photo, they can and usually have several colors and are complex. The problem is that if you try to scale them up or down too much they fall apart. That's their big downfall, they also have really big file sizes.
NOW, consider a vector as a piece of paper with mathematical instructions on it telling us to 'draw a line from this point to that point', simple. You can scale a vector up or down almost infinitely. Vectors usually have less colors and smaller file sizes. If you make graphics it's good to have them both. if all you do is edit photos you don't need a vector program. Personally, I can't get by without having both, they each have their uses, strengths and weaknesses.
Thanks sweetheart....very clear way of putting it