More in depth about the BigInt Data type in Java Script

I have just started learning js, and also programming in general, i am on the “data types” lesson. On the lesson it self there are 7 data types, but in the Java Script documentation code academy provides there is an eighth one called “BigInt”. Can someone describe its use, what connection does it have with the number " 2^53-1" and why there is an “n” in the “9999999999999999n” example?
Thanks in advance.

It looks like you can only operate on it with other bigints, use it in conditionals and use || and other compare operators on it. Learn more here: JavaScript data types and data structures - JavaScript | MDN