terminology: "l-value" & "r-value"

[spir]

Hello,

I'm bluffed by the 2 terms "l-value" & "r-value" used in C-line language common terminologies. I think I guess what they mean, but I don't understand the need for such absconse idioms. Why not:
	l-value <-> variable
	r-value <-> value (or expression)
?

I guess (*p) is considered an l-value. Indeed, it's a special way of denoting a variable, matching the special case of a pointer. If correct, this requires slightly extending the notion of variable (and/or of identifier).
On the r-value side, I cannot find anything that makes it a distinct concept from the one of value, or of expression.

Explanations welcome, thank you,
Denis
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