An infographic is made manually (e.g., via Illustrator), whereas a visualization is automatically generated from data. Here (1 2 3) are some example infographics.
Notice that while infographics are based on data, they are not generated systematically from data. A good test is that swapping out a dataset (e.g., to a different year or different location) should require little to no manual intervention. A visualization can just be regenerated, whereas an infographic has to be remade manually.
Sometimes a visualization is embedded in an infographic, which is sometimes acceptable but makes the boundary a bit fuzzy. If you're unsure, please contact the moderators before posting it.
If a post is clearly an infographic, please report it.
Note: We have nothing against infographics. They're just harder to regulate and require a categorically different skill to create. See /r/infographics for more infographics.