Pound/Hashtag/TTT symbol?

I am quite new to Lua, so I was scavenging through the example code and I found this:
local n = #array
What does the “#” do? I looked all around the reference.

The hash # gives you the number of numeric items in the table. As long as the items are all in number order, it should give a reliable result

You can also use it to add items to a table, eg tbl[#tbl+1]=“abc”, which adds an item using a table index one greater than the current table count.

It won’t give you the right answer if you have gaps in your table (eg no tbl[3]) or if you have text keys in your table, eg tbl[“abc”]=3. In these cases, you are better to loop through your table using the “pairs” approach.

It will also return the length of a string

Cool! Thank you all for the help.