But I also read some examples of a lightning url which are lnurl followed by a long incomprehensible string, not a neat email address like thing as my example above. 

Are these two similar? Or am I mixing up lightning url with lightning address? Which one to use for payment? Any tutorial describing the difference between these? 

> Any website that asks for lightning url to pay/refund me, I can post that account name there and I should be able to get my sats?

Yes, for example SN, see [/wallets](/wallets)

> Also, I read that sending lightning requires a predetermined amount, as in, the receiver has to key in the amount to generate the address and must give it to the sender. Is my understanding right? But in that sense, my coinos account violates that?

A lightning address is a way to request an invoice from a lightning node. Instead of you generating an invoice from your node for the recipient, you give the recipient your lightning address so they can generate an invoice from your node themselves.

Read more here: https://lightningaddress.com/

Under the hood there is a specific invoice generated, but it’s facilitated by the sender and your LN address provider, no manual intervention needed by the receiver 

You are correct. With a lightning address, anyone can send you any amount. You don't need an invoice for a specific amount

bitcoingecko

 and got what looks like an email address 

So, is that a lightning URL, that anyone (even those without a coinos account) can send me sats from their own wallets? Or does that serve a different purpose? I am not exactly clear how to use that wallet. Any website that asks for lightning url to pay/refund me, I can post that account name there and I should be able to get my sats?

Also, I read that sending lightning requires a 

 has to key in the amount to generate the address and must give it to the sender. Is my understanding right? But in that sense, my coinos account violates that?

bitcoin_beginners

So, I made an account on [coin os](https://coinos.io/) and got what looks like an email address `<username>@coinos.io`. 

So, is that a lightning URL, that anyone (even those without a coinos account) can send me sats from their own wallets? Or does that serve a different purpose? I am not exactly clear how to use that wallet. Any website that asks for lightning url to pay/refund me, I can post that account name there and I should be able to get my sats? 

Also, I read that sending lightning requires a _predetermined_ amount, as in, the _receiver_ has to key in the amount to generate the address and must give it to the sender. Is my understanding right? But in that sense, my coinos account violates that? 