2.1 versus 5.1 home theater

Both of these numbers refer to the speaker set up of the home theater.

2.1 represents two front channel speakers (left and right) and one LFE (low frequency effects) channel, otherwise known as the subwoofer.

5.1 surround sound is just that: you are surrounded by speakers. You have your left channel, right channel and subwoofer (as in 2.1) but you also have a center speaker and two surround speakers (generally in plane with your seating position or slightly behind it).

For real 'Home Theater' applications, 5.1 surround sound is going to provide you with the better movie watching experience. All modern movies and in fact most DVDs (and Blu-Ray etc) have 5.1 surround tracks on them. By playing these movies on a 2.1 home theater, all of the sound that would go to the center speaker or the surround speakers is played only by the front two speakers. A 5.1 surround system versus a 2.1 system will draw you into the movie and give you a better experience.

All standard definition television content is broadcast in stereo and for this, there is no benefit of 5.1. For home theater applications, however, 5.1 is the way to go.