Tell us about the "+" in the email?

+ and all that on it before the @ is simply ignored. It is very convenient, because it allows you to have one box countless addresses.
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For example, I often use this feature when you register for some websites, for example facebook e-mail myemail+fb@domain.net for yandex — myemail+ya@domain.net for some dubious website — myemail+hrenkakayato@domain.net etc.
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Letters to all these addresses will be delivered to myemail@domain.net
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And then if for example in my drawer starts to come spam in the name myemail+hrenkakayato, it is immediately obvious where the leak is. And easy to make a filter to just ban such letters...

Pro plus can only say that the Google-mail, sent to ivan.ivanov+spam@gmail.com will fall in the drawer ivan.ivanov@gmail.com.
The same applies to points gmail their cuts. There is no difference between the boxes ivanpetrov@gmail.com, ivan.petrov@gmail.com and iva.n.pe.tr.ov@gmail.com ;)

I have been using this trick. Very convenient to set up filters in gmail.
For example, I myself sent an email to myemail+notes@gmail.com and it is archived under the label "Notes".

This is an optional filename extension, which is used for easier filtering and sorting of IMAP-mailboxes on the side of the recipient. This is not supported by all mail servers. For example, GMail supports, and the postal service on MS Exchange there.