Ok, I could use a little help with these retirement plans... I have FOUR plans showing up at Fidelity, only two of them have $$ in them. I'll admit it, I'm confused as to what these plans are, why some have $$ and others don't. Please be gentle, I never had a 401k or pension or DC or any of this in the military, and the shorthand names for these things in all my reading is just confusing me more. Can anyone give a brief rundown on why 4 plans exist with two empty?
Thanks

1. Delta Pilots Defined Contribution Plan (401k) -- has $$ in it, got $300 in 2012 so far.

2. Delta Pilots MPPP (401k) -- has $0 in it.

3. Delta Pilots Plan (401k) -- has $$ in it, got $50 in 2012 so far from employer contributions.

4. Delta Air Lines, INC. (401k) -- has $0 in it, no contributions


I keep reading " the Delta Pilots Plan" or "the DC plan", which don't match any of these names exactly... thanks.