What is the difference between the
\def commands in TeX/LaTeX?
Ideally please provide a simple example that will illustrate the difference between them.
The difference is in the time at which the ‘right hand side’ is evaluated.
This is a simple process.
However it's also a subtle one, so it might be worth highlighting a few key points:
While the existing answers are all true I like to highlight one point which wasn't explicitly mentioned yet. I myself got this information recently from Joseph Wright (see his answer and our comments in Simple un-obfuscation of some LaTeX internals).
As Michael said
They're pretty completely different.
creates a new command
copies the commands from the