Aseprite is described as '(previously ASE, aka Allegro Sprite Editor) is a program to create animated sprites & pixel art. Sprites are little images that can be used in your website or in a video game. You can draw characters with movement, intros, textures, patterns, backgrounds, logos' and is a popular Image Editor in the photos & graphics category. There are more than 50 alternatives to Aseprite for a variety of platforms, including Windows, Mac, Linux, Web-based and iPad apps. The best Aseprite alternative is Pixelorama. It's not free, so if you're looking for a free alternative, you could try Pixelorama or PixiEditor. Other great apps like Aseprite are Piskel, Tilf, GraphicsGale and Grafx2.
It's not a pixel editor, you literally cannot edit pixels with this software.