By using nonbreaking hyphens, you can prevent certain words from breaking at all—for example, proper names or words which, when broken, become unattractive fragments. By using nonbreaking spaces, you can also keep multiple words from breaking—for example, clusters of initials and a last name (P. T. Barnum). If you apply the no‑break attribute to text longer than a line, InDesign compresses the text so that it fits on one line.
The Nonbreaking Space varies in width depending on point size, the justification setting, and word space settings, whereas the Nonbreaking Space (Fixed Width) character maintains the same width regardless of context.