This is what I have its 2.4 A per port. 8 A overall.
I'm confused as to what your title has to do with your text, but anyway...
Is this true?
Yes.
Also, how can we use products like this: http://www.amazon.com/gp/product/B00GTGETFG/ref=s9_al_bw_g107_i1 If devices use different amounts of power, how can these products exist? Do they just have a large amount of power, more than any 5 devices could possibly use, so they just take what they need, or what?
This product puts out 40 W at 5 V, as described in the title. This is 8 A total. So, the sum total of all power drawn by all 5 devices can be no more than 8 A. A tablet will usually use about 2 A these days, and a newer phone will use over 1 A. So, if you're not charging 5 tablets, you'll easily have enough power to charge your devices. Charging 5 tablets won't work well though.
I use This to do all of my usb charging, works great
I bought this. It's probably a bit overkill but will charge 4 iPads looking at the specs. http://www.amazon.com/dp/B00GTGETFG/ref=cm_sw_r_udp_awd_N7nQtb0B14E95