2 I propose that...

That's the bottom line of a proposition. In the context of logic and mathematics (as opposed to politics), a proposition is not a proposal to act or change. Instead, a proposition is a statement with at least one subject (stating who this is about), and a predicate (what about who). A proposition can be true or false.

``Tak has a healthy level of triglyceride.''

This proposition is not true, as Tak has at least twice the ``red line'' concentration of triglyceride.

In mathematics, $6=2$ is a proposition (the equal sign interpreted as equality check, not assignment). It is false, obviously, but it is a proposition.

Note that a proposition must have a value of true or false all by itself. As a result, $x=4$ is not a proposition, because its truth value depends on the actual value of $x$.