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An op-amp is an integrated circuit. Like all ICs, they are generally treated like a black box for the desired function, which is where most of the answers in this thread are coming from. Since you are complaining about "abstract" answers, I'll guess that what you want to know is how it is actually implemented within that IC. The answer is generally a series of stages of active circuits (read: circuits using transistors, BJTs or FETs), centered around a differential amplifier circuit and typically having input buffering, intermediate gain stages, and output stages. Answering this succinctly in a 4chan post is kind of like answering succinctly "Wtf is a CPU". Opamps are far less complicated of course, and also analog rather than digital, but basically I'm basically just trying to whet your appetite and point you in the right direction. If you want to know more, Sedra & Smith's Microelectronic Circuits contains a detailed chapter on opamps, as well as many preceding chapters which detail the components (transistors and their configurations) that you'll have to be familiar with in order to understand.
If you're just some Circuits 101 retard who's struggling with the topic de jure, literally all you have to know is Vout = A*(V+ - V-) where A is assumed to be infinity, no current flows into the input nodes, and the output is limited by the supply rails. The rest of the operation can be logicked out from these principles if you're not a moron. If you can't reason through why V- is forced to be equal to V+ by negative feedback given these assumptions, transfer into women's studies.
