The SU-30 (The original version, not the MK) is a 2 seat advanced interceptor, that was designed to lead and manage air combats, in a way its like a small AWACS.
The SU-34 (formerly known as the SU-32FN, among others) is a tactical ground attack a/c. It was designed to replace the aging SU-24's of the Russian AF. The SU-34 is a two seater (unlike the SU-30, the pilots of the SU-34 seat side-by-side), it is heavily armed, and designed to penetrate the enemy's defense in low altitude. The SU-34's cockpit also includes a washroom and a food cabinette.
Feel free to ask more questions about the SU-27 family.
Yeah I'm sure its the SU-34 now. This a/c had many designations over the years:
First it was the SU-27KM-2, which was supposed to be a training version of the SU-27K (now known as the SU-33), the pilot and instructor seats were put side-by-side to improve safety when a trainee would be landing on an aircraft carrier, it provides the same view to the instructor and the trainee.
Then, it became the SU-27IB. The first SU-27IB was actually an SU-27UB that had its whole front section replaced to accomodate the different cockpit. The SU-27IB was designed to be a ground attack a/c to replace the SU-24.
Later, it was renamed the SU-32FN, probably because it needed an attack aircraft designation rather than a fighter one (see my reply to the "SU-42" post).
Finally it was named the SU-34.
I don't think they ever actually made a carrier trainer, did they???
And yeah, the carrier trainer was quite different from the eventual SU-34, I included it on the designation list because it looks like the SU-34 program was a direct result of the carrier two-seater program.
The trainer was made, it is called the Su-27KUB. I am not sure how many Russia has thought, if they have any. Apparently the side by side cockpit was used because it is a lot better for carrier training.