“Virual Memory is Low”

What does it mean when I get an error that says “Virtual Memory is low” and how do I fix this. I did try to change my Virtual Memory by right clicking my computer going to properties. Then going to the Advance tab then clicking Settings in the Performance section, then selected Advance and then in the Virtual Memory section I said Change. And I changed the intial to be the same size as the Maximum size and then restarted.
Please help me and let me know how to get rid of the error.
Thanks in advance!