It tackles about "suspend blockers" or what we call "wakelocks". Android's Power Management.
Take time to read whenever you have time, I'll quote...
The Google's Android operating system has been designed with mobile devices, like cell phones or tablets, in mind. Such devices are generally not expected to be able to carry out CPU-intensive computations or do very I/O-intensive kind of work like workstations or servers. Thus, although they are supposed to allow their users to preform some tasks that can also be done on a desktop computer, like browsing the Web, reading and sending e-mail, listening to music or playing simple video games, they generally need not support extensive multitasking and they are inherently single-user. Generally speaking, their performance requirements are quite dierent from the performance requirements of other Linux-based systems.
On the other hand, it is essential that these devices can be used for as much time as possible without connecting to any external power sources (e.g. AC power). In other words, their battery life has to be as long as reasonably possible, even at the expense of performance.