1) There is no difference between filters and photoshop filter, filters are usually used to give photo effects, and enhance the contrast as well as the brightness. For example: lomo effect, beach effect, and sunrise effect. But in photoshop you can customize the effects using curves or by using the photo filter option in the menu bar.
2) Usually if you sharpen an image the pixels which constitute to make the image start emitting RGBA(stands for red,blue,green, and alpha) in a high rate. Simply the pixels start to pixelate.
3) blurring effect is the opposite of sharpening it smoothens the image and the image starts fading away.