I briefly looked into it, but I can't seem to figure out what to make with it. It looked like you couldn't write an application with any portability, and any user would basically have to run a smalltalk vm to use your application. Am I mistaken?
I'm no expert (not even close), but I believe they'd have to run Pharo itself, yes. So you could redistribute the Pharo runtime along with your app code (similar to, say, Python).
Anyone interested in playing around with Smalltalk can use https://pharo.org - I recently tried it and was pretty amazed with the quality of documentation available. It is quite a different experience working in an interactive live environment.
You may be able to build web applications too (http://seaside.st/).