Difference between two Lamba Expressions in LINQ - vb.net

Question

I am trying to understand the difference between these two Lambda Expressions within LINQ Join method.
The two lines I do not understand are those starting with Function(aaa) ... and Function(bbb) ....
Why do I have explicitly name the field Name in the second example for both aaa and bbbwhile in the first one it works without it?
On the other hand in the first example bbb.Owner points to Owner field of Pet but it does not tell that Name field of the Person shall be used to make the join.
First example (comes from .Net Framework documentation with variable names changed):
Structure Person
Public Name As String
Public SecondName As String
End Structure
Structure Pet
Public Name As String
Public Owner As Person
End Structure
Dim magnus As New Person With {.Name = "Hedlund, Magnus"}
Dim terry As New Person With {.Name = "Adams, Terry"}
Dim charlotte As New Person With {.Name = "Weiss, Charlotte"}
Dim barley As New Pet With {.Name = "Barley", .Owner = terry}
Dim boots As New Pet With {.Name = "Boots", .Owner = terry}
Dim whiskers As New Pet With {.Name = "Whiskers", .Owner = charlotte}
Dim daisy As New Pet With {.Name = "Daisy", .Owner = magnus}
Dim people As New List(Of Person)(New Person() {magnus, terry, charlotte})
Dim pets As New List(Of Pet)(New Pet() {barley, boots, whiskers, daisy})
Dim query = people.Join(pets,
Function(aaa) aaa,
Function(bbb) bbb.Owner,
Function(ccc, ddd) _
New With {.OwnerName1 = ccc.Name, .Pet1 = ddd.Name})
Second example (my code)
Structure MyObject
Public Name As String
Public Value As Integer
End Structure
Dim Test1 As New List(Of MyObject) From {
New MyObject With {.Name = "a", .Value = 1},
New MyObject With {.Name = "b", .Value = 2},
New MyObject With {.Name = "c", .Value = 3}
}
Dim Test2 As New List(Of MyObject) From {
New MyObject With {.Name = "a", .Value = 11},
New MyObject With {.Name = "b", .Value = 22},
New MyObject With {.Name = "c", .Value = 33}
}
Dim Joined = Test1.Join(Test2,
Function(aaa) aaa.Name,
Function(bbb) bbb.Name,
Function(ccc, ddd) New With {
.Name1 = ccc.Name,
.Value1 = ccc.Value,
.Value2 = ddd.Value})

Answer 1

IF you look at the documentation, you'll see that the first function is the selector for the outer sequence and the second is the selector for the inner sequence.
The value form the inner and outer selectors must have the same type (TKey) and will be compared using the default comparer for that type (there's an overload that allows you to pass a comparer).
The third function is the result selector that receives a TOuter and a TInner instances that match according to the selected keys and returns a TResult value.
So, in the first example TKey is Person. outerSelector and innerSelector must return a Person, thus aaa and bbb.
On the second example you chose to compare the Name field and not the entire MyObject structure.