Many people have been asking me what I mean when I say "post processing". Post processing is everything photographers do before sending a photo to a client or posting it online. It includes white balance, sharpening, adjusting curve and levels, and maybe some photoshop. In short, it's anything that will correct or enhance a photo.
Is it necessary to do? Yes it is. Modern DSLR cameras use a file format that saves all the details from the scene in front of you called RAW (you still can shoot in JPEG if you want). Unlike point and shoot cameras where the camera does everything for you and save the photo in small JPEG file.
By shooting in RAW you telling the camera not to do anything to the photo and you will be the one who will take care of correcting and enhancing the photo.
Now, what you do with your photos will be different base on what type of photography you do and what is your subject. For example, if you shooting a portrait of a person, means your work flow will not only include correcting the white balance and sharpening but also retouching face and body. It's also differ if it's a man or a woman (women take way more time). Every photographer has his own working flow that he/she more comfortable with.
The most important thing about post processing is not to make it so obvious in your photo. Make it look like you didn't touch it, this is the hard part about the whole thing.
This is an example of what post processing do. The photo below is the kind of photos that I'll dumb because it's not good not even after processing but I thought I'll use it as an example here.
Work flow applied here (or what I remember of it):
1- Correcting what balance. I always do it first.
2- Removing unwanted distracting objects.
3- Increase the saturation for some colors in the building.
4- Sharpening some areas, not all the photo.
5- Adding the final effect which is some grain, desaturation, yellow and green color cast.
Post processing is what makes that amazing photos you see online so amazing.