What is meaning of Initial Size 0 in internal table ?

Hi SAP-ABAP Experts .

I have created a internal table like this

i am not understanding the role of Initial Size key word .

What is meaning of Initial Size 0 ?

If do not give this then it (Internal tabe)also works same way ?

TYPES: BEGIN OF t_ekko,

ebeln TYPE ekpo-ebeln,

ebelp TYPE ekpo-ebelp,

statu TYPE ekpo-statu,

END OF t_ekko.

DATA: it_ekko TYPE STANDARD TABLE OF t_ekko INITIAL SIZE 0,

PLease explain it .

Best regards : rajneesh