Can you explain what does the "?" and "&" means? Should it be ";" instead?

arg = "mailto:" & Toadrs & ";" & Toadrs1 & ";" & Toadrs2 & ";" & Toadrs3 & ";" & Toadrs4 & "?" & _
"cc=" & Ccadrs & ";" & Ccadrs1 & ";" & Ccadrs2 & ";" & Ccadrs3 & ";" & Ccadrs4 & "&" & "subject=" & encodedkenmei & "&" & "body=" & body