Since the goal is complete customization, plots are created by composing sets of simple objects. If you're new to Biggles, I suggest taking a look at the examples first. Containers are things like plots and tables, and can be turned into graphical output. Components can't be visualized on their own, but only when added to containers.
Containers can contain other containers.
TeX emulation Biggles includes a simple TeX emulator which recognizes subscripts, superscripts, and many of the math symbol definitions from Appendix F of The TeXbook . Normally, Python strings are interpreted as C strings.