Instantly in this case means several things to me (person who wrote the copy). 1) Very quickly create precise diagrams, meaning diagrams where you know things a

Instantly in this case means several things to me (person who wrote the copy). 1) Very quickly create precise diagrams, meaning diagrams where you know things are perfectly snapped, aligned, etc. 2) Very quickly see the changes you make to your diagram reflected in the drawing (i.e. you don't just see the outline of geometry when moving an object, you see the entire object). 3) Very quickly make your diagrams in code, if that's what you like to use, with the live-edit program mode. Other small things factor into this choice of words as well. For example, native embedding of LaTeX equations can be a big timesaver for someone who needs many of them. Or, using the "duplicate in grid" tool to quickly make rows of boxes connected with arrows. I hope it doesn't come across as misleading. I really do believe Vexlio can allow you to create diagrams much more quickly than its competitors.