There are now 59 people who have achieved an official average in under 6 seconds and almost all of them seem to use one speedsolving method.
That is the CFOP method, or variants thereof.
The basic CFOP method consists of solving a cross on one of the sides, some people only solve the cross on white or one other fixed colour but most top speedcubers are colour neutral (able to start on any colour) these days. The solver then solves the first two layers at the same time, this can be done by matching up the relevant corner and edge pairs and inserting them between the correct centres. Then the solver moves on to OLL which stands for orientation of the last layer, this is where the bottom face is solved but not necessarily the bottom layer, there are 57 algorithms for this step and everyone at the top who uses CFOP will know them all with ease. Finally, the solver does PLL which finishes the cube off, there are 21 algorithms for this step and many of the top cubers will know multiple algorithms for each case so they can choose which one will be fastest at that exact time.
All of the top 13 for 3x3 average as of writing this use CFOP, however, number 14 is Sean Patrick Villanueva from the Phillipines and he uses Roux, Roux is a different method preferred by a small minority of top speedcubers that involves solving a 2x3x1 block on one side and then solving another 2x3x1 block on the opposite side, the solver then is able to solve the corners of the last layer on top with slightly shorter algorithms as the M slice is free to be moved around, finally the solver finishes the cube off with just M and U moves in a step called LSE (last six edges), if M moves (turns of the middle slice) count as one move, then Roux is a more efficient method, however, it is often more difficut to fingertrick the steps as fast, so most top cubers use CFOP which has easier case recognition and more fingertrick friendly algorithms.
While most of the top cubers for regular 3x3 use CFOP, for 3x3 one handed, Roux has become far more dominant with 6 of the top 10 solvers using Roux, this is likely due to its lower movecount and the development of table abuse, where the solver rests the cube against the table to do M slice turns with one hand.
