"lvalue" is an expression that refers to an
object (which can have (a) value(s) within it), and "rvalue" is an
expression that only has a value (ephemeral value as Chris Torek would
claim) and no association with an object.

As far as their use, an "lvalue" that refers to an object of type T,
can be used anwhere an "rvalue" that that has a type T can be, but not
vice versa. So if one uses an lvalue that refers to an int variable in
an context that requires an int value, then simply the value sitting in
the object is dumped into that context.

In simple terms:
lvalue means expression that can be used on the left hand side of an assignment.
All lvalues can be used as rvalues. Reverse isn't always true.

lvalue means a variable which is used in left hand side of '=' assignment operator...
e.g- x=5....
rvalue will be in right hand side...

Lvalue(LEFT Value) and RValue(RIGHT Value) are desired through the Assignment Operator(=).
Left Side of the Assienment operator is LValue;It must be one Variable Name.
Right Side of the Assienment operator is RLValue;

Ex:
a = j + 8^90;
a is Lvalue;
j+ 8^90 is RValue;