For what purposes I can use PNG file?

Portable Network Graphics (PNG) is a bitmap image format and can be used for websites, email templates, and simple documents such as Word.

PNG file format is a compressed format, but unlike other image formats, your logo design does not lose image data so there is no blurring or smoothing. Simply stated, your logo design is reduced in file size without reducing image quality.

PNG image format provides greater color depth - up to 24 color bit.
PNG image format also allows transparency. This means that you can apply your logo design on different colored backgrounds or photos without keeping it in rectangle shape.

Learn more about PNG file format ...