Well, taken literally, QRP is a Q code that means to reduce your transmitter power. It can be a question, or a statement.
Like many things, it's a relative term. An operator that normally operates with a kilowatt amplifier may say that operation without an amp (100w output or so) is QRP. And for them, it would seem that way. But for me, who never uses an amplifier, 100W is not QRP, it's maximum output.
The way I've always heard it, and interpret it, is that QRP operation means a transmitter output of 5W. Somewhere along the way, someone coined the term QRPp, which means lower than 5 watts output. I've never seen an authoritative definition of what that actually means, but I suspect it means an output of 1 watt or lower.
Now how do you get to QRP? Seems to me there are two ways to do that. One is to build or buy a minimalist rig that produces not more than 5 watts of RF output. The other is to take any rig, and turn down the RF output to 5 watts max. In a contest situation, that might be a better choice, because a normal 100W rig probably has a better receiver, with more interference fighting features, than a minimalist QRP rig.
Which of those methods is best for you? Again, it depends. If you're operating from home, and available power isn't an issue, then take the normal rig and turn down the output power to get to the 5W level. But if you're operating away from home, and you have to carry your power source with you, then you may want a power sipping minimalist little radio to extend battery life and operating run time. Got solar? Then extending battery life is no longer an issue, so maybe you use the normal rig with the better receiver. It's all a trade off, and you have to decide which method is best for you given the circumstances, and the various operating constraints those circumstances will present.