Understanding `@eval` help string and expressions

General Usage
1

I came across this implementing the rotational cipher in exercism with the very nice help of @tomerarnon. The help for @eval states:

@eval [mod,] ex
Evaluate an expression with values interpolated into it using eval. […]

Not knowing what an expression is I looked into the Julia docs for expressions and evaluation where my interpretation is that an expression has the form

quote
    CODE
end

However, @eval evaluates

@eval CODE

rather than

@eval quote
    CODE
end

To give an example

name = "pln"
@eval quote
    function $(Symbol(name))(txt)
        println(txt)
    end
end

returns a quoted version which can be passed to eval to evaluate

name = "pln"
@eval function $(Symbol(name))(txt)
        println(txt)
    end

creates the function pln as expected.
I am not fully clear on what the type of CODE is. Is that also an expression even though it is not quoted?