There are real differences among the formats and some formats really are better for certain applications. For example, if the file needs to be high quality but very small, JPEG is good. For maximum quality, RGB is a good choice. For maximum compatibility, GIF and PPM are good choices because they are very broadly used. For printing, PostScript is the clear standard and often you must convert your file to PostScript before printing it (or the printing software will do it for you). The list of formats and specific advantages goes on and on so use that format which is best for your individual application.
Some of the image file formats as follows:
JPEG, GIF, BMP, PCX, PIC, TIFF, PSD, etc.

Converting Images

The first thing to understand is that there are many image formats and hundreds of software programs capable of converting images. Many of these image formats are native to one specific graphic application and are not offered as an export option in other software.
Not all image formats are compatible with one another. In general, we can almost always convert between bitmap formats and from vector to bitmap. This is as simple as opening the image in just about any image editor (or image viewer) and choosing the Save As command. For instance, the Microsoft Paint program that comes with Windows can convert between BMP, JPEG, and GIF formats.
When we try to convert from a bitmap to a vector format, things get complicated. To convert a bitmap to vector, we need special software called tracing software. Bitmap format is actually a colletion of thousands of pixel, so when we try to enlarge it, the picture will become bad. Tracing is a process to change from bitmap format into vector and there is no guarantee that we will have the exact appearance of the image.