I don't understand the logic of how doing #Tab + 1 is adding something?

I don't understand the logic behind this

local Tab = {}

Tab[#Tab + 1] = 'Value'

for i,v in pairs(Tab) do
	print(i,v)
end

Why do you have to put #Tab number of Tab + 1 why cant you just do Tab + 1

I heard this is also similar to table.insert

Putting # in front of a table will return the number of objects it has in it. If you did "Tab + 1" it would be like "{} + 1". But doing #Tab + 1 is like doing "0 + 1" since there are currently no objects in the table!

#TableName gets the number of objects in the table. TableName returns the table.