TikZ/PGF — Vector Graphics & Diagrams

CTAN: https://ctan.org/pkg/pgf
Manual: texdoc tikz (~1300 pages)

Setup

\usepackage{tikz}
% Load libraries as needed:
\usetikzlibrary{arrows.meta, calc, positioning, decorations.pathmorphing,
  patterns, shapes.geometric, shapes.misc, fit, backgrounds,
  automata, trees, mindmap, circuits.logic.US}

Basic Drawing

Minimal Example