Why does Apple include a No Access option? Within this same area, you can add other users. Some you may wish to grant access to, while others you may want to keep strictly out. If you're afraid that Margie's feelings may be hurt by comments regarding her work ethic, assign her No Access privileges for that folder.
Printer Sharing: At one time, if you wanted to share a printer with other computers on your network, you had to purchase a model that sported an ethernet jack and then incorporate the thing into a wired network. Those days are long gone--and not only because many printers today support Wi-Fi. You can share printers that have no wireless capabilities whatsoever. And the way you do it is with the Printer Sharing option.
Simply connect your printer to your Mac in the usual way (that's most often via a USB cable), enable Printer Sharing in the Sharing preference, and choose which printers you want to share across the network. (You may have just one or more than one.) The printer you select will appear as an option for any Mac on your network. (You can also choose to share a printer from within the Print & Scan preference.)
Advanced sharing options
We now venture into options intended for advanced users. Rather than confuse you with a lot of technical terms and convoluted explanations, I'll lay out the gist of what the remainder of the sharing options do.
Remote Login: This sharing option allows you or other people to gain remote access to your computer's files. To do so, they use something called the Secured Shell (or SSH) scheme. This scheme requires that the person attempting to log in know the username for the account you wish to access, the account's password, and the computer's IP address. (I discussed IP addresses when I discussed setting up your network.) As with File Sharing, you can choose to allow anyone in who has this information, or you can restrict access to individual users that you specify.
The advantage of remote login is not only that it lets others on your network gain access to your files, but also, through a bit of configuration magic that I won't go into now, that it lets people on the Internet outside your local network do so. Unless you know what Remote Login is for and have a specific need to enable it, leave it unchecked.
Remote Management: I've already discussed the Screen Sharing option. Remote Management is quite similar: It allows people on your network or across the Internet to view and control your Mac remotely while connected to your computer via a VNC (Virtual Network Computing) client. Again, you must choose who can have access to your Mac. And also again, if you don't understand or need this capability, leave it off.
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