[intro.execution] p7 says

Evaluation of an expression (or a subexpression) in general includes both value computations (including determining the identity of an object for glvalue evaluation and fetching a value previously assigned to an object for prvalue evaluation) and initiation of side effects.

Consider the sentence in the parenthesis

determining the identity of an object for glvalue evaluation

This is exact the definition of glvalue per [basic.lval] p 1.1

A glvalue is an expression whose evaluation determines the identity of an object or function.

It could be understood that the evaluation of a glvalue is a kind of value computation. However, the emphasized part is a bit strange:

fetching a value previously assigned to an object

This sounds like the duty of the lvalue-to-rvalue conversion. What if an expression itself is a prvalue(e.g. 0 + int{1};)? Shall we just say

fetching the value of a prvalue for prvalue evaluation(i.e. computes the value of an operand of an operator)

This is one function of the evaluation of prvalue

A prvalue is an expression whose evaluation computes the value of an operand of an operator, as specified by the context in which it appears

It is not sure whether the initialization of the result object of a prvalue takes account to be the value computation? After all, we just define the side effect as

Reading an object designated by a volatile glvalue ([basic.lval]), modifying an object, calling a library I/O function, or calling a function that does any of those operations are all side effects

We define "modifying an object" with the cross-reference to ([expr.ass], [expr.post.incr], [expr.pre.incr]), in [dcl.type.cv]

Any attempt to modify ([expr.ass], [expr.post.incr], [expr.pre.incr]) a const object

however, they are not about initialization.