The precise name of a symbol in mathematics sometimes depends on what you're using it for. For example, × is often referred to simply as the multiplication sign, but if you need to distinguish scalar from vector multiplication, you might refer to it more specifically as the cross multiplication sign, vector multiplication sign, or something similar.
In your second example, the ・ symbol is called dot. The product of two numbers multiplied using the dot operator is the dot product. In some contexts, you might call it the scalar multiplication sign.
Outside of programming, we usually only use * for multiplication when we can't type ×. The * symbol is usually called the asterisk or star, though if you're using it as a multiplication sign, you might call it that, instead.
The last example appears to be using a period. Like *, I assume this is simply because they couldn't type ・. I could call this a period, but more usefully, I could call it whatever it represented: in this case, I might call it dot, since it's standing in for ・.
If so, what about an example as ti metaphor?
My favorite example of a metaphor is a computer's interface.
A computer stores information as collections of zeros and ones. Early computers were driven by punchcards to represent this, and it was incredibly difficult to learn.
To make it easier, someone used the metaphor of a traditional paper-driven office to explain what was happening inside the computer.
Don't think of your document as a set of zeros and ones - metaphorically, it's a file. Don't think of that fike as being stored on a magnetic disk - metaphorically, it's in a folder.
Although it's not strictly true, it is meaningful and useful.
Best Answer
Technically, it's the multiplication sign, ×, not x. It indicates a hybrid name, one that indicates the plant or animal is a hybrid. The Wikipedia entry begins by saying
so the scientific name is saying "this kind of Mentha that we call piperita is actually a hybrid of other things."