assert expression in release mode

[drug via Digitalmars-d-learn]

Before I lived in assurance that asserts are actual only in debug mode 
and in release mode they are nothing (except `assert(0)`). But today my 
whole life is going sour because I stumbled upon assert in release mode 
and of course that assert is failing.

This doc https://dlang.org/spec/expression.html#assert_expressions say 
nothing about debug mode vs release mode.

So the question is when and why assert expression is enabled in release 
mode (besides assert(0))