1) Periods are used to concatenate the string. This just means that it will put them together, as one peice. "hi"." there" = "hi there"
2) Add another <td> at the end. <tr> is a row, and <td> is a column/cell in a table. You should really learn HTML before trying PHP, unless you're just trying to install something.
3) I use echo, but printf can be used equally as well. Look at the docs for information.