CH3-C(=O)-CH2-CH3
Proper English name is 2-butanone (butan-2-one)
2-butanon is its German and polish name.
It is an organic compound which belongs to a group called ketones. It is used widely in industrial chemistry to produce various synthetic compounds. If you would like to know more try http://en.wikipedia.org/wiki/Methyl_ethyl_ketone or http://webbook.nist.gov/cgi/cbook.cgi?ID=78-93-3