Cyclist for about 40 years. Maintain and set up a fleet of 25 police bikes. Repair and refurbish bikes for re-sale....
Anyway.... Someone with no real background wanting to "get into" cycling faces a confusing array of types, styles, and prices these days.
First thing to ask...What do you intend to do with the bike? Cruise around the neighborhood with the kids? Ride the local rails-to-trails? Commute? Serious fitness training? Bombing through the woods on tough trails?
Essentially, you can break the myriad of bikes into three styles.
1. Roadsters. Bikes intended to travel on pavement, and at decent speed. They have narrow, high-pressure tires, "drop" bars, and so forth.
2. Mountain bikes. Intended for off-road use, they feature fat knobby tires, low gearing, tough components, sturdy frames, etc.
3. Hybrids. Also called "fitness" bikes and "comfort" bikes these days. A road-type frame with mountain-bike type components and intermediate tires.
A possible fourth category is what companies are calling "urban" bikes.... Think of a mountain bike with road tires.
Of these, the hybrid is a good choice for many casual riders. Upright riding position, easy to control, reasonably capable on pavement and also handles "improved" trails pretty well.
Also, they tend to be cheaper...
Almost all of the major brands will try to put out a bike at all "price points". They are as alike as peas in a pod. You are looking at a spec-built frame, manufactured in China (often in the same plant) with various brand-name components bolted on.
It's only when you get up into expensive iron that you get made-in-the-US frames and deluxe components.
In the price range you mention, you should be able to pick up a fairly decent major-brand hybrid or fitness bike. I just sold a very nice Trek for only 250.00.
Make sure it fits! A good shop will help you pick out a properly-sized bike.