Answers given so far have talked about matrixing and encoding display data into binary data lines, but these signals are not compatible with the actual display hardware. The wording of your question implies that you are asking how does the display data get to the individual pixels of the display, and the existing answers don’t elaborate on this at all.
The display data in RAM is converted to a stream of binary data which may take many forms, and the panel controller is then tasked with decoding this stream and ensuring each pixel of the display is activated to the appropriate level as specified in the binary data. You’re right to say that there’s not 2m+ outputs, and for a colour full HD display this figure is actually 6m+, 2m+ for each of the primary colours. Some displays even have 4 or more colours per pixel, so 8m+! But individual signals for each pixel do exist physically, let me explain.
The actual interfacing from controller to panel is matrixed, meaning that the rows and columns of pixels are interconnected as shown in this (simplified) diagram:
This is a 4x4 display having 16 pixels. To activate the top-right pixel for example, power is supplied to the wire on the first row, and to the wire on the fourth column. In practice, the rows are powered in sequence and the columns receive their signals simultaneously corresponding to the required status of each pixel in the currently powered row. In this way the entire image can be built up a row at a time. In the case of a 1920x1080 full colour display, the panel controller will have 9000 output wires ((1920+1080)x3). Not 6m, but still staggeringly complex. The controller is usually tightly integrated with the panel, as every panel type is unique and requires very specific signal timing and voltages.
The most amazing part of this system is that the final electronic components that actually supply the power to the LCD elements are printed right on the panel along with the pixels. This is what the “TFT” part of some panels means, thin-film transistors that form a part of each pixel. These are shown in the above diagram. Their job, along with other thin-film components of the pixel, is to maintain the state of their associated pixel until the panel controller has completed the full panel scan and returned to the pixel to update it to its next state.
Even though the data supplied to the display panel assembly may consist of binary encoded data in the form of perhaps a 16 bit wide parallel data bus, or even a two wire serial stream, it does still eventually become individual signals numbering in the total amount of pixels in the panel. It’s just that they actually only exist right at the location of each pixel.