Like you have brain, heart, lungs, stomach, a computer has a Central Processing Unit, Hard Disc, RAM, CD/DVD Drive, and other input output devices.
Now you have seen how bulky a desktop used to be, and how sleek a laptop is. So its like compressing capabilities of an elephant and lion into a human size!
First result of such compactification is heating. If your laptop gets hot by continuous use for two hours, buy a heat sink or a cool pad for base of your laptop.
Laptops are portable, and hence we carry them from place to place. Now, if you carry a laptop while it is switched on, even in the sleep mode, it is bound to damage the hard disc, which keeps rotating even in the sleep mode. So if you carry it in sleep mode while travelling, the reading-writing head might brush up extra on the hard disc and cause mutual damage. So always switch it off and then carry.
Using a scratch guard for the screen and a dust guard for the keypad will tell you how much damage you have saved for these, when you look at these guards after a year. It keeps the original things intact.
Laptop reads a CD/DVD with a pointer tip. Now if you run two applications based on a data DVD, e.g. one of copying a file, and other of playing a song on the DVD, then the tip has oscillate rapidly between the two different locations on the DVD where these data are stored. This slows down the two applications, and more disadvantageously, it can damage your DVD Read Write Head.
Battery of Macbook is expected to last for 1000 cycles. 1 cycle means complete charging and total discharging. To make best use of battery and enhance its life, charge it fully and then let it discharge fully.