Crapware refers to any program that is included in a PC's initial software package even though it does not benefit the end user. The definition of crapware can change from one user to another, because while some might want a particular program, such as an anti-virus utility, a disk defragmenter, or a game or other app, to someone else, these programs serve no purpose and make the computer run more slowly.
Some discussions of crapware revolve around large anti-virus or security programs added by original equipment manufacturers by default. Other kinds of crapware include games and promotional apps, as well as other kinds of programs that have very limited use. Some of these programs are set to run on boot-up and throw pop-ups onto the screen.
Cleaning up crapware involves uninstalling programs and removing any "scraps" off of the computer drive. Programs like CCleaner and PC Decrapifier can help. Challenges in erasing crapware involve potential problems with a registry, and completely untangling elements of these useless software programs from whatever else is on a PC drive. Some tech companies have tried to offer crapware removal services for a fee, but these have generally been unpopular.