Usually the laptop is purcased when the user needs the portability, when he wants or have to do the same thing as he does on a desktop but somewhere else. Somewhere where is not the space to put his PC or there is not the time to unplug all the cables, to carry the hard drive, the monitor and the keyboard. You know the drill... it's a hell more easier to put a laptop or a netbook into a bag and to continue your work in other place: your office, your client office, a bar, the bearch, and so on. Considering the weight of the laptop, for most of the people anything over 1.5-2.0 kg is going to be tiresome and impractical - in that situation the portability is not something that they can aquire.
In the situation when the portability is a requirement, but you don't need too much processing power you can use a netbook: a computer with lower specifications and lower cost solutions (a cheap computer) that help you to browse the internet, to read emails, to edit documents and so on. A kind of computer that can help you move your office wherever is power and internet connection... and peace of mind to be able to work. Keep in mind that the notebooks are ultaportable, but they do not have CD/DVD drive and they have limited connectivity options (no SD/MMC card slots, 1 USB and rarely a monitor out port).
If you need a family laptop, something you can do a lot of things (browsing the internet and your pictures, opening documents, sharing pictures and other information with other people, playing some games) you don't need a powerful laptop (in matter of processing power and resources). The medium-sized screen means you should be able to transport this laptop to different rooms of your house or your office, but they are not likely to be portable enough to take out of the building for extended periods.
For the average user the most common configuration for a laptop would be 4 or 8 GB RAM, Intel i5/i7 processor and 500 GB or 256 GB SSD hard drive. For those intending to use their laptop as a gaming or graphic design setup (images and videos) you will want at least 8GB RAM, i7 processor, a minimum of 1TB hard drive and 512MB graphics card. The gaming and graphics laptops can be compared with the desktop in the matter of the processing power, but into a more flexible format. Multimedia laptops speaks for themselves: they are intented to watch movies and do whatever you want to do with more screen (15 inch plus screen) and processing power.
You should consider that in some situations you can not replace the desktops and your laptop will "scream" requiring more resources (RAM memory and hard disk space). And, one of the most important thing: more processing power you get, more energy it drains from the battery. So you should not start using the laptop to play or process large quantity of data without an external energy source.
