If a site hosts a server, can it use my local files?

My server is almost prepared for the public, but I'm not sure if I should create a static IP (Is it better? If it is, can I know the reasons?) or get it hosted (know a good site?).

If I did get it hosted, would it create a brand spanking new world, or is it possible to upload your files? I do find it very unlikely, though.

Thanks in advance!