Basically, my mask slows or limits how far my breath travels. That and maintaining a safe distance will limit the chances of me passing it on.The issue lies in which type of mask. If it’s a single layer cloth mask the pore sizes are pretty much non-existent and really don’t do a whole lot due to almost everything you are able to expel through your breath at least will pass through and due to no real pores it will go both ways. You can get multiple layer masks which are a slight improvement but it relies on it being almost like a web, and made of differing materials, you can get medical grade masks like this that must be proven to catch 95% of water droplets however the virus among other things could still pass through. If you have a medical grade mask containing membrane depending on the pore size it will catch some of the stuff you will breathe out or in depending on which way the membrane works. If people are really worried you should invest in these although they won’t be cheap.
The rest is googled science showboating.