psd A .psd extension file is an image file created with the help of Adobe Photoshop. PSD is the default extension used for saving a Photoshop Image which can have either a single or multiple layers which can be worked individually even after having saved the file. The file can also be saved in other formats like .jpg, .tiff, .gif or other imaging formats but if a user wants to edit the individual layers later, it is necessary to save the .psd file without overwriting it while converting it to another format. Converting a .psd extension file into an image file in another format flattens the image so that it can be viewed as a regular image. The images created using this extension are of a very high resolution and the quality in terms of clarity is extremely good as compared to other commonly used image formats like .jpg, .png or .bmp.
ico The .ICO filename extension refers to the ICON image file format originally developed by Microsoft. The extension is used to represent computer icon images of varying sizes designed for the operating system Microsoft Windows. Its use today has extended to developing icons for programs designed using the Microsoft developer's suite Visual Studio and other applications. Similar to other device independent bitmap file formats, the ICON file format is also in the raster graphics class of image formats where each individual pixel is part of an orthogonal dot matrix data structure with support for a limited palette of color information. As a resource file, the .ico file format has its strength in contextual use. This allows for multiple icon images of different color depth or size to be stored within the resource file and used when appropriate.