In lcd or plasma tv, what is meant by series? Whats d difference in the series? Example Samsung series 3 n 4?

Series are different lines/models by a given company. All the major manufacturers have various series of TVs which help group the models. It allows consumers to know which models carry which features.

One given series does not apply to all brands no. Each brand has its own series breakdown which will vary from its competitors. Examples,

Samsung Series 3, Series 4, Series 5, Series 6, Series 7, Series 9 and in LED Series 6000, Series 7000, Series 8000.

Sony lines are letter based, there is, L, M, S, V, W, Z, and XBR

Panasonic lines are letter and numerical based, C1, C12, U1, S1, G1, G10, G15, V10, Z10. The letters mean more than the numbers though with Panasonic.

LG uses numbers and letters as well, LH20, LH30, LH40, LH50, LH55, LH90, SL90

I've listed all of the above from lowest end series to the highest end flag ship series. So with Samsung the LED 8000 is their best, with Sony the XBR is their best, with Panasonic the Z series is their best (though the G and V series are of near equal quality actually), and with LG the LH90 and SL90 is their best.

Series 3 and Series 4 represent Samsung LCD HDTVs entry-level sets for 2008. In total, these two series comprise 15 sets, eight under the A450/A451 and seven under the A330/A331.

Models in the A451 and the A331 have identical specs to their counterparts in the A450 and A330 series respectively except that these come in gloss white finish instead of the standard black color found on the other sets. Sizes range from small 19-inch sets to medium-size 40-inch LCD HDTVs;

well, its just the next line of product by the manufacturer for the same model

Electronics models, like ipod nano series, iphone series, etc...