GIF for images that contain 255 colours or less. Else JPG/PNG.
You can use an image viewer like Irfanview to save the image and use the proper image setting to save as a PNG. Or the same with an image editor like GIMP.
Its not Photoshop PNG but rather PNG-8 file format. Use it to save files with limited color palette (max 256) to have file with smaller size for Web which can contain and transparent areas in image.
png
PNG is an image file format, such as JPEG or BMP. One of the differences between PNG and JPEG, is that PNG supports transparency.
youus ask bummie
GIF and PNG 8 file formats.
PNG image 80x80 pixels
PNG image 80x80 pixels
There is no simple answer, the answer depends on the image contents and on the number of unique colors in the image.For photos jpeg is the best option, compression is lossy, but for the human eye the differences are not that dramatic. You can adjust the compression level (some tools allow it, some not).For small images, with a maximum of 256 colors .gif or .png are good. Both use loss-less compression.You can use an image converter to test some of the possibilities (gif, png or jpeg).
No, it will not be harmful to your computer.
PNG