The ‘All Mail’ folder in Gmail is where Gmail keeps all of its emails and labels are applied to show emails in various folders including the Inbox. So the ‘All Mail’ label is really an archive folder in Gmail.
On the other hand, only non-archived incoming emails are in Gmail Inbox. Thus, the following emails are not included in Gmail Inbox:
Sent emails
Archived emails
Promotial emails
Social emails
Forum emails
Chats