How to turn text into Icon or symbol

this is a question related with icon.

Please visit : Symbolset.com and try out the demo section.

Now my question is, how could we produce something similar with this symbolset, Let's say I have a vector glyph in Illustrator and exported it into SVG. How could I make it works like symbolset.

When people type "love", it's turned out into Heart icon.

If you know the answer, please give me a clue