How to read tikz/pgf and tcolorbox manuals

Question

When reading the tikz/pgf and tcolorbox manuals there are often lines of the form (these are just examples)

/tikz/current point is local=⟨boolean⟩

/tikz/cs/radius=⟨dimension⟩

/pgf/number format/sci zerofill={⟨boolean⟩}

/tcb/titlebox=⟨mode⟩

Although it is clear that /tikz/ and /pgf/ are there to separate commands that are available in tikz and in pgf respectively, it is not completely clear what this notation mean and what significance it has to the end user. For example in tcolorbox a lot of lines seem to start with tcb but not all of them.

I cannot find any explanation of this in either manual. Does anyone know what these lines are and how to interpret them?

Irrelevant comment: I do find both manuals excellent, but one issue with reading them as a beginner is that most of the examples are not particular pure. Instead of just including the command that they want to illustrate they most of the time include a lot more. Often this additional things appear much later in the manual which makes it very hard to read.

Answer 1

You may think of /tikz, /pgf and /tcb as directories, and /tikz/cs and /pgf/number format as a subdirectories. You could, for instance, say

\pgfkeys{/pgf/number format/.cd,fixed,fixed zerofill,precision=2} 

to switch to /pgf/number format directory, and then set the fixed, fixed zerofill and precision=2 keys (this example is from p. 1049 of pgf manual v3.1.5). Among other things, these directories allow us to avoid running out of name space.

So from

/tikz/current point is local=⟨boolean⟩

you learn that

1. current point is local is in the /tikz directory (and not in /pgf, say), and
2. it is a boolean, meaning you should feed it with true or false (but not dimensions, say).

Answer 2

TikZ ("TikZ ist kein Zeichenprogramm") is the frontend layer with a special syntax, making the use of PGF easier

PGF ("portable graphics format") is the basic layer, providing a set of basic commands for producing graphics

From my perspective pgf is the coal-tar which leads to the production of the road(tikz) -- with tikz you can enter the the waypoints to get to the final destination

While the previous systems (picture, epic, pstricks or metapost) focus on the how to draw, TikZ focuses more on the what to draw.

A summary of commands at -- Summary of Tikz commands -- reproducing all the commands would mean reproducing the manual itself

Rather than reading the manual better to start experimenting with the code itself will have better results in understanding syntax variation

A nice example of tikz/pgf differentiation -- How can I use pgf from within TikZ