Welcome to AA!
1. For optimum growth of the Anacharis, you should have no lower of lighting then Moderate lighting (around 2-3 watts per gallon)
2. kelvins are a measure of how our eye should precieve the "blueness" of a bulb( 5000 to 6700k is the best area for freshwater tanks).The extra blue they put out helps make up for the red that is lost by the water absorbing it, and helps the tank from looking yellowish / greenish. Anything over 6700k will make your freshwater scene look washed out or faded (the exception is a 9300k bulb from All-Glass that has special phosphors to balance out the colors, I've heard great things about it.)
3. Flourecents are long bulbs like you would see in an office building...cfl's are Compact Flourescents, same thing just the size of a normal light bulb all coiled up.
will be able to support some plant, even reef (I use a Marineland double bright LED
lighting system on a moderately planted tank). They use lumens instead of watts. The only bad thing I see with them is the price, they are pretty expensive at times.....
5. I believe they are referring to kelvins when they say that, how many K
does the bulb have that you seen?
6. How many watts does the desklamp hold?