To open it, simply double-click and it will display the file’s contents in TextEdit (or the text editor of your choice). By default, the hosts file is relatively simple. It contains a number of lines of descriptive text which are “commented out” with the pound or number sign (#). For each line, any text after the pound sign is ignored by the computer, making it a good way to add notes and descriptions to your files. It also contains default IP values for localhost and broadcasthost. To edit the file, you’ll add your own lines after broadcasthost.