GnuPG (gpg4win) - what is the difference between Key-ID and public key and certificate (*.asc)?

Question

Encryption

Good time! I installed gpg4win - everything works, I managed to sign the picture of the email. signature and then verify its authenticity. I read the FAQ on GnuPG, learned how to create a revocation certificate and export the certificate, I can view the public key through the console and make a backup copy of the private key, but with all this I UNDERSTAND THAT I DON'T UNDERSTAND ANYTHING :( I
smoked the theory, like the basics of asymmetric encryption understood ..
... but I don't understand point blank: 1. What is this very "certificate" that I can export using Kleopatra to a file with the extension .asc
and is it secret?
is also displayed in Kleopatra - should it be hidden too, or vice versa should it be posted on the site?
3. How does public-key relate to all this and how does it at least look like? Is it the same as a certificate? With it, they can encrypt the data for me, as I understand it, but I did not understand which of them was the Public-key.
Please help me figure out which one is which.
Thank you.

Answer 1

What is Key-ID

key-ID is the tail of the key's fingerprint. A fingerprint is a unique identifier for a key, it can be used to find the key on a public server or identify it in gpg commands. It is he who is checked at the key-signing party. 8 digits is considered small by today's standards, it is better to use 16.
For example:

gpg --fingerprint --list-keys F83FA044
pub   4096R/F83FA044 2012-05-28
      Key fingerprint = 2B67 854B 98E5 327D CDEB  17D8 51F9 CC91 F83F A044
uid                  Max Filippov <[email protected]>
uid                  Max Filippov <[email protected]>
uid                  Max Filippov <[email protected]>
sub   4096R/161A72EA 2012-05-28

I don't know what can be exported from Kleopatra, but .asc is just ascii text. Any key or set of keys can be exported to ascii by adding -a to the export command.
It looks something like this: gpg -a --export <key-id>
Having it, you can encrypt the message for the owner of the corresponding secret key.
It can be sent to the key server or sent in text form to the sender of the message. The sender can import it from a key server by key-ID or from text.