at mixing studios there's monitors and..

[savk01]

at mixing studios there's monitors and another pair that i don't know what they do, they usually put them next to each other, so basically you have two "monitors" on the left and two on the right?

whats the difference between each pair? thank you

[Softsynth]

Not a necessary product at all.
Those smaller speakers can be for checking the final mix on a low quality limited bandwidth, say radio friendly (miss highs and lows) source, mimicking cheap stereo systems or car stereo etc.
Alternatively just take the recording out to the car, or the kitchen stereo......

[dea-man]

Check mixes in as many different environments as possible (Car, computer, earbuds, TV, listen from another room, boombox, whatever......).

[DVDdoug]

A pro recording mastering engineer is going to use good monitors that he's familiar with (in a room he's familiar with).

If you see two good monitors, they are probably used by two different engineers. Or, there are often "big" monitors used for impressing clients and musicians, rather than for critical mixing/mastering.

If you see one pair of cheaper monitors/speakers, those are for checking the sound on a cheaper setup. Auratones and NS-10's are famous examples of this. But, most engineers will also take the mix out of the studio and check it in their car, on earbuds, their TV, etc.