The official one is .ico or it can also use .JPG but the JPG file will look a little messed up.
Icons.
Typically, a document or file is opened using an icon that resembles a page or a piece of paper, often depicted with a corner folded down. This icon may also include a pencil or a pen to signify editing capabilities. Additionally, file icons can vary by file type, such as a Word document (DOCX) represented by a blue document icon, or a PDF file shown with a red PDF logo.
An icon.
If it is an mp3 file (the most common type for downloaded music) you can play it in iTunes or Quicktime - you can drag the song file's icon onto the iTunes icon in the dock to load it. Try double clicking on the song file's icon and see what it opens in.
An icon is a logo for a program
In order to open a DJVU file, you will need to double click on the files icon. From there, your computer will locate a program that can open this type of file.
"ico" is a common extension for an icon. An icon is the image you see in a file browser or on your desktop. That icon will represent a file.
An icon.
.ico
Open your image with an image editor (photoshop, gimp, ...) that supports saving as an icon.First you have to resize the image to a size that is compatible with an icon. For example 32x32 or 16x16 pixels are typical icon sizes. Then you have to reduce the number of colors to 256. Now your image has the properties of an icon and can be saved to an icon by File/Save As/ and select the icon type.
first make your icon in paint then save as an ordinary file (.jpg) then use the online tool , favico maker and upload your image. The online tool will make it an icon file then it gives you the option to download it
A widget is a screen graphic or icon. A file widget, also known as a shortcut, is an icon containing a link to a file. Clicking it causes the file to open.