Every digital photo gets subjected to post processing software.
Note: the image sensor in a digital camera is an analog device, and the image sensor cannot record color. The image sensor only records luminosity.
So, every digital photo starts as just gray scale information.
The individual pixel voltages generated when an exposure is made are analog values that have to be converted to digital values in the camera.
Analog pixel voltage values go in one side of the analog-to-digital (A/D) converter (on or near the image sensor), and digital pixel values come out the other side. What may have been 12,963,283 discrete analog pixel voltage values gets reduced to either 4906 (12-bit depth) or 16,384 (14-bit depth) discrete digital values.
If Raw is the selected file type, the digital pixel values get written to the memory card and post processed outside the camera in Raw conversion software be it camera maker software or not.
Raw conversion entails substantial post processing - demosacing, colormetric interpolation, gamma encoding, sharpening, anti-aliasing, and tone mapping.
If JPEG is the selected file type, the post processing software used is in the camera.
What started out as a Raw file can be converted to JPEG outside the camera after Raw conversion.
Adobe Photoshop, Adobe Photoshop Elements, and Adobe Photoshop Lightroom all use the same Raw conversion software application - Adobe Camera Raw (ACR).
ACR first appeared with Photoshop 7. The current release of professional grade Photoshop is CS 6 (Photoshop 13). CS6 Camera Raw, Elements 11 Camera Raw, and Lightroom 4's Develop module all use ACR 7 for Raw conversion. (Elements uses a de-featured, consumer grade version of ACR.)