Monospacing is when a font uses the exact same visual space for every character – including all punctuation and symbols.
This is an example of a monospaced font.
When contrasted to a proportionally spaced font (such as this one right here)
monospaced fonts have a distinctive look and feel because of their mechanical and precise nature. Most fonts in use are not monospaced. Typically, proportionally spaced fonts are more aesthetically pleasing as they flow more naturally and collapse negative space. However, monospaced fonts can be extremely useful for such things as text based charts, guitar tabs, and ascii art to name just a few. Programmers love monospaced fonts because it makes it easier to organize lines of code and spot inconsistencies.
Here is an example of a November 2017 calendar created with a monospaced font:
Mon | Tue | Wed | Thu | Fri | Sat | Sun | | | 1 | 2 | 3 | 4 5 | 6 | 7 | 8 | 9 | 10 | 11 12 | 13 | 14 | 15 | 16 | 17 | 18 19 | 20 | 21 | 22 | 23 | 24 | 25 26 | 27 | 28 | 29 | 30 | |