Vim for full Select function

have been looking to see if there are quick ways to Select all , but many of the web is repeated, and the wrong, such as:
1, $y, what is this? To write also written: 1, $y, but I tell you, write: 1, $y is all copied, not a full selection
DG, this is more misleading, this is the deletion of the cursor row to the last line of content (including the cursor row of the content)
Where the above is going. The correct answer to all of the choices is:
Ggvg
Explain the above command a little bit.
GG allows the cursor to move to the first line, the vim is valid, VI is not valid
V is entering visual (visual) mode
G cursor moves to the last line
After the selection of content can be other operations, such as:
D Delete the selected content
Y Copy the selected contents to register No. No. 0
"+y Copy the selected content to the + register, which is the clipboard of the system for other programs

Vim for full Select function