I am planning to buy Novation Launchkey midi controller. But I am wondering if I can play this keyboard just like other ordinary keyboard by just connected to power ? Is it mandatory that it to be connected with a drvice to play sound? Can it store midi waves and enable them to play while we are travelling? I really don't want to do a lots of configuration and connection just for playing it. Would it work just like other keyboards?
No, it has no sounds in it and it won't make any sounds on its own - it can only control another device (usually a computer) via MIDI - that other device is what makes the sounds.
This is typical of keyboards that are called 'controller' keyboards or MIDI 'controllers' - they can only control other devices.
Many normal keyboards with sounds can also be used as MIDI controllers, however. It sounds like a normal keyboard with sounds and MIDI may be what you need instead.
To elaborate on topo morto's comment, you can connect a MIDI controller to a "sound module." Sound modules are made by lots of different companies with all sorts of different features and sound sets, but they are basically just a box that you plug a MIDI controller into that sends sounds out.
So a sound module can take the place of the computer.