How to use Pen

Basically you can use it to draw straight lines and B splines. You get anchor points and handles around that point to control the tangent vector and curvature at that point (curvature can be one sided).

http://www.automotiveillustrations.com/tutorials/adobe-illustrator-paths-pen-tool.html

Mesh and Mesh Gradient Tool.

Equation and Special Math Symbols

Use Latex to label figures in Illustrator

Import Latex Fonts into Illustrator