Is it something i can use to send email?
Is it an mx record which can filter spam for incoming emails?
Is it a service which i can use to send email forms directly from my website?
Is it SMTP service?
Is it an IMAP/POP service?
Is it still the same email routing with new fancy name?
Email Routing is a service where you can set up an MX record where all incoming email is forwarded to another server.
Now, imagine the code running that accepts that email and forwards it to another server. That’s Worker email. You can set up an MX record where all the email goes to your Worker. Instead of going to Cloudflare’s code that does a lookup and sends it to some other server, your code can do whatever it wants with that email.
So… no, it’s not something you can use to send mail. Yes, you can use it to filter email, if you write all the code to do that filtering. No, it’s not for forms from your website. Yes, it’s SMTP service, but probably not in the way you’re thinking. No, it’s not POP/IMAP service. No, it’s not the same email routing with a new name; its you being able to write code to do a thing like what email routing does.
I don’t know much about rspamd but no, you can’t just run whatever you want. It’s a Worker. The Worker gets your email and decides what to do with it. So it’s something you can run in a Worker, meaning Javascript or WASM code that will run in that environment.
Yes, it’s an MX record, but Cloudflare does not offer mailboxes so your Worker can either forward your email on to someplace else, do something with it locally (like add it to a database), or drop it. It’s not a mail-receiving service. It’s a service where you can write your own code to handle incoming email. If you’re not sure what that means, it’s probably not something for you.