Wifi devices showing my SSID 3 times.

Question

Hello.  First off, let me say I am new here and have only some experience setting up wifi, etc.  I apologize in advance if this question has been asked before or is something simple I've overlooked.  Wireless devices are showing 3 SSIDs.  I am using 2 airport extremes.  I purchased this newer model in March or so (MD031LL/A 802.11 A/B/G/N Model No. A1408 with simultaneous dual band 802.11n "and twice the range of 802.11g."  I previously had the MB053LL/A (Model NO. A1143) 802.11n also. 
I had been running the new model fine, not completely certain all of my settings were optimal, but no major issues, except the 2nd floor of my house had problems dropping out at times, and I have, like many people now, a wireless printer, ipad, iphone, appleTV, wifi bluray, TV, and one MacBook Air  (1.7 ghz mid 2011) and a Macbook Pro.  After some slowing which may or may not have been related to upgrading to Lion, I bought the new AE and things seemed to improve, or maybe the settings were just new, I don't know.  Lion also had several updates.  I ramble, I apologize. 
So I decided rather than selling the old airport extreme, I was told I could use it to extend my network.  So I placed it on the 2nd floor and set it up to extend my network.  Things seemed okay, and the new AE had 2 SSIDs, 'orange 02 and orange 02 5ghz'.  I don't understand how this works, or which I should be connecting to, but again I digress.  I need to read up on this.  So I had to setup my bluray for wifi and it listed 3 networks (2 'orange 02' and 1 'orange 02 5ghz) 
If I go to the 2nd floor there is still a corner that is a dead spot where nobody can get wifi, but luckily we don't go in that area often.  But computers on the 2nd floor seem to lose the internet connection randomly (wifi bar shows it is connected) and so I reconnect to a different SSID, 5ghz usually.  Or sometimes it's the otherway around.  Right now, since our central air decided to stop working in 95F heat, we are downstairs, closest to the new AE and all using the orange o2 5ghz. (see screenshots below)
What am I doing wrong?  Why is it showing this extra SSID, how do I know what to connect to and is it possible my settings are not right?  My apologies for rambling and perhaps not using the right questions or researching this more on my own, but I did google this and it linked me to a question (unrelated) on apple support dicussions.  If anyone has any answers or insight, please reply.  I want to learn.  I can provide screen shots or whatever info you need.  Or perhaps I'm not able to use the older Airport Extreme as a way to extend the network.  I also am very confused about the whole 5ghz, etc.  When looking at other wifi networks around me, I do not see any others listing as duplicates.
Thank you,
Izaq (Davin)  (please be kind, this is my first post)
p.s. screen shots below
also, current speedtest.net (connecting at a nearby server) showed 11ms ping, 35.97 Mbps download and 6.48 Mbps upload. (not sure how that ranks for the amount of devices I have)
and this screen shot from Wifi Explorer:

Answer 1

Wireless devices are showing 3 SSIDs
The new AirPort Extreme is broadcasting two bands... one 2.4 GHz and the other at 5 GHz using the same wireless network name, or SSID, so that is where 2 SSIDs are visible.
Wireless devices will automatically connect to the best signal quality from either band depending on their capabilties.  An iPhone, for example can only connect at 2.4 GHz. A newer laptop can connect at either 2.4 GHz or 5 GHz, so it will pick the best signal...automatically.
The third SSID is from the other AirPort Extreme that is extending the signal from the first. This is an older single band device, so it can only extend one band. If this device were dual band, you would see 4 SSIDs.
The AirPort Extreme upstairs is automatically extending the strongest signal that it receives, which is likely the 2.4 GHz band since these lower frequencies are stronger than the higher frequency 5 GHz signals.
Everything appears to be normal according to the information in your post.