Why do I need a static IP-address?

First of all for this purpose that to your computer it was possible to receive access from Internet. Generally, when you incorporate with Modem server it is already possible to get access to your computer  (More precisely, only to those resources of the computer to which you have wished to open access). But for this purpose it is necessary to know a name of your computer or it IP-address. Therefore the user who will want to install with you Connection (for example on FTP protocol) will not know a name of your computer. It is necessary to mark that "dynamic" of the address does not influence in any way your operation, If you initiate  connections with other computer:  The remote computer automatically knows the address of your computer (and its name) Also can inform these given to a remote user.