OS X 10.7 (Lion) introduced a feature called the Character Picker. This allows you to press-and-hold a key on your keyboard, activating a little popup with the different character options associated with that key. This can be a useful feature for some, as it allows you to visually see all of those additional character options and not have to know how to otherwise activate each of them. I, however, found that it was more of a hinderance to my workflow. For example, when I am editing my code in VIM or Vintage Mode in Sublime Text, this feature prevents me from holding down the movement keys (h, j, k, l) to navigate. So I decided to disable it.
Adding spaces in your Dock on OS X is a nice feature that allows you to bring a little bit of visual organization to your icons. It is really easy to accomplish in just a couple short steps. First, you will want to locate your Terminal application. Terminal can be found at
Applications > Utilities > Terminal. Or, for a little shortcut, you can hit
Command + Space on your keyboard. This will being up Spotlight and you can then type in Terminal (or the name of any other application you wish to find) and it will show it up in a list below the search input.