...

"..." Is a easy to type 3 letter string,

It has multiple meanings one of them being:

"i dont know how to respond to this."
it can also mean:
"im bored so please talk to me"
or "i wanted to type something but i dont know what"
It is also rarely used for "just stop you're anoying".

The expressionless face:(😑) is a emoji that can have the same meaning as "..."

just one dot (".") can mean:
"i dont know how to respond to this."
or "i wanted to type something but i dont know what".

if there are more then 3 (4 to 5) dots then it will mean the same as the three dots but a little more aggressive
If there are more then five it means:
"Im trying to anoy someone with spamming"

If you see a ".." it means: "i accidentally put two dots while i ment to type one."
The reason why its not: "i ment to type three dots."
is because you don't misspell: "..." you type it with passion and passion can't be misspelled

"..."