Pixlr is a nice little editor that serves as your small, but handy replacement for big monstrous image editors by Autodesk or its competitors. Despite being small and light, it's as useful as any other, more serious tool.
Pixlr has a nice, if slightly dark interface with the main features immediately on display. You can open an image you wish to edit, then work on it using the tools available, both in the menu toolbar on top and the working toolbar on the left. In the main window, you can access the image's metadata. Not only can you crop, rotate and resize the image, but you can also refine it by adjusting definition, contrast and clearness. Then you can add various effects to the image, controlling and adjusting colours, contrast, etc. There are options to add various overlays in order to make the picture layered and more complex, combining different effects for a result that you would find beautiful. Additional, more technical tools allow you to adjust transparency, add or remove layers, etc. There are no advanced settings you would find in a more feature-rich commercial editor, but the ones that are there work nicely.
Pixlr provides the option to define and adjust borders by selecting one of the well-designed templates available, add stickers to specific parts of the image, write texts over the image, etc. There's even the option to share your image online using the built-in sharing tool.
Pixlr is light, fast and reliable. It's one of those editors that lack the heavy-hitting features of bigger, more expensive alternatives, but do great in their smaller field.