Wow. I can see why you are confused. Maybe it's easier if we separate the different FUNCTIONS.
Many cd players just have "line out," meaning they cannot control the volume of the signal. Therefore, you need a volume control, and if you have more than one source you need something to switch between sources.
A pre-amp provides volume control and switching. Yes, it will also amplify really-low level signals like those out of a record player if the preamp has a "phono preamp", but it sounds like you don't need that. So think of a preamp as volume control and source switching (between a CD player, a dvd player, a tape player, for example).
Now, some CD players have the ability to control volume, so you could by-pass a pre-amp and go directly from the CD player into the amp. But you couldn't switch between any other components this way, and the volume control on the CD may reduce the quality of the sound.
A pure amplifier has no controls - it takes the low level signal from a preamp and makes it louder.
An integrated amplifier is an amplifier combined with the switching (sometimes) and volume control of a preamplifier. You could plug a cd or dvd player's analog output directly into an integrated amp.
A receiver is an integrated amplifier with a radio built in.
Now lets talk about digital. What is recorded on your CD are pits representing zeros and 1s. Lots of them. Something needs to convert those numbers into analog sound that can be amplified and heard. Your CD or DVD player has a built in DAC that converts numbers to analog sound. Many players are also capable of outputing numbers (called digital output) into an separate outboard DAC to do the conversion from numbers to sound. And you also can put a dac into a receiver or preamp and let it do the conversion. A digital receiver takes the numeric output from the cd or dvd player, converts it to analog, allows you to control volume and switching, and contains an amplifier.
All of these components are made in different qualities and for different prices. What is important is making sure that the equipment you buy will work together. There are many ways of outputting digital audio, and you need to be sure that your dac (or receiver) has a matching input.
So, if you just want to connect a dvd player to a pair of speakers, you would likely want to buy either an integrated amp or receiver (using the analog out of the dvd player), or a digital receiver (using the digital out of the dvd player into the dac of the receiver). You will need cables to connect the components, and speaker wire to connect the speakers to the amplifier.
Does that clarify the situation?