The browser is designed to generate random-ish functions as series expansions to a given order, and is able to display the "Julia sets" of these functions, at a given square resolution. Technically, what's displayed on screen is more of an approximation of the Fatou components of the function. If you don't know what these are, there are details about it in the manual.

The computations leading to such approximates are mostly done with numpy vectorization, so it can get CPU heavy real quick at not so high resolutions. I'd advise only using the browser to find interesting functions, and then view them using the explorer.

The frctlexplorer is designed to view .frctl files exported directly from the browser. A .frctl file only contains the image at export time, the function's NumPy array, and metadata such as the colourmap or series expansion order.

The computations in the frctlexplorer are done by a GLSL fragment shader that is directly available to the users, to allow customisation of the shader computations for GLSL afficionados. Some lines of code are commented out in this one, precisely to make this task easier on users who want to experiment, such as a comment containing a mouse-controlled complex variable c that can be placed anywhere in the function's definition, or hls-compatible functionalities.

These are obviously a lot easier on the computer since they're handled by the GPU. However, the default use for the iTime uniform is iteration count, so the long the program runs without pausing, the slower it'll get. Please be wary of this and press pause (P) when you think the program is starting to get too slow.