Abstract Simultaneously (Also known as 'Opened but closed')
Give me to someone,
And I am closed,
Wait for response,
And open it goes.
Words I have three,
And everyone knows me.
Though abstract, I am,
If you agree,
Anyone can use me,
Does someone know: Who is this so-called 'me'?
It might be a bit easy for some of you, but it's a 100% original one.
The answers can be a little different, but as long as the core answer stays the same, it's good.
Some information for line 7/8 (Though abstract, I am, if you agree):
I am abstract, but I am used in the non-abstract place named 'The Universe'.
And with the last line (Who is this so-called 'me'?) I mean: What am I?
EXTRA INFORMATION (Required for a 'good' answer)
I may be abstract, but some theories say I am both abstract and a type of waves.
HINT to speed up the process:
Look at @can-ned_food's answer and the comments attached for a hint!