I have this obsession to begin cycling. I borrowed a bike from my brother and rode one day and was hooked. I learned a couple of things that afternoon on my own.. the bike was heavy and bulky and apparently too tall for my 5'5 frame and the seat far too skinny for my liking.

i began the next day searching the web for information.. but either i stink at searching the web or i don't know what i am searching for. there was all kinds of information but i can't seem to swim through it and glean what i am needing.

Please answers these questions for me so that i might move forward with this obsession:

I would like to think I might ride every other day 6 to 8 miles. i live in the city and expect to be on concrete. Obviously I am new to this and worry about putting alot of money into a hobby that I may not stick with. So my first and most important question:

Where do i get a "good enough" starter bike for $200 or less?

and from there...

what is a hybrid, a comfort and a cruiser bike?
why are some tires very skinny and some have more traction similiar to mountain bikes?
does the size of the tire make a difference in the ride?
do i want to lean over or sit up straight?

i am 42, in decent shape and normal weight, but gym's bore me.. the thought of riding for exercise seems alot more interesting.. but i want to make the right choices.

please help me so that i will buy the right bike.