Queries use the SQL language, and program code uses VBA, so they are two different things.  SQL was invented by IBM in the 70s, while Visual Basic (predecessor of VBA) was invented by Microsoft in the 90s.

VBA is a "general-purpose" programming language, one that can be use to make different kinds of applications.  But SQL is strictly for relational database systems like Access, SQL Server, MySQL, etc.

In Access, you can use VBA expressions within SQL:

    SELECT * FROM MyTable WHERE MyDate <= Now();
    (Now is a VBA function, thus a VBA expression)

or work with SQL and queries within VBA:

    Dim r As Recordset
    Set r = CurrentDb.OpenRecordset("SELECT * FROM MyTable WHERE MyDate <= #" & Me!DateField & "#;")

In the query design screen, the expression inside the criteria box is *not* really a valid expression.  It is the actual SQL statement, shown in the SQL window, that counts.  For instance, the criteria box may let you type something like:

    =>X And <=Y

but the actual SQL criteria, as shown in the SQL window, should be:

    field1>=X And field1<=Y

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