Space is a major element of design that will be used everywhere in your design and it’s not limited to typography!
Leading is an important term that refers to the spacing between the horizontal lines of type (for historical background go to: https://en.wikipedia.org/wiki/Leading).
When it comes to headlines and titles, you may either use a lot of space between lines for a more quiet and calm composition or use less space to give your composition more stress and energy. In either case, legibility is imperative.
As seen below, two posters designed by the brilliant Paula Scher are using leading in a creative way to help not only convey a message, but to engage people to go to the ballet and theater.
Body copy, on the other hand, should be judged by eye. Too much space between lines or too little space can make your message hard to read. If you can read it comfortably, so can your reader.
TIP: Be honest with yourself as a designer…even if your design looks “cool,” always ask yourself, “Am I effectively communicating my message?” If the answer is, “ehhhh” then it’s time to revisit your design….Again, be honest!