In Arabic it is called Riyaa. the origin of the root word (ra'aa) translates as
- to see
- to behold
- to view
the word Riyaa means
- eye service
- hypocrisy
- dissimulation
- dissemblance
In the prospective point of view (islamic of course) it means;
to perform acts which are displeasing to Allah, with the intention of pleasing other than Allah
and this is exactly why, it is important that our conducts are to be guided by a good or pure intention - that is for the pleasure of Allah
“Learn about intentions, for their importance is greater than the importance of actions.”
Yahya Ibn Abu Kathir
Trying to purify your intention cannot be done without knowing the reason why you are doing what you are doing.
Taking the example from the time of the sahaba (may Allah be pleased with them) Prophet Muhammad sallallahu alayhi wa salam said
"whoever migrates for the sake of Allah and Prophet Muhammad (s a w) his migration is accounted for the sake of Allah and Prophet Muhammad (s a w); and whosoever migrates for the sake of this world or to marry a woman (his migration will not be for Allah and the Prophet Muhammad (s a w), and will be accounted only for the purpose for which it is intended (Bukhari and Muslim)."
source:http://www.workingmuslim.com/articles-blog/3-faith/20-dont-show-off