Using the web isn't the same as knowing what the difference between a web browser and a computer OS is. Most people don't buy personal computers anymore, politicians are likely only using office PCs and their phone.
Even if I didn't know the word 'train' I think most reasonable users of English would still agree that I know what a train is.
People who use a browser to go on the web, even if they don't know the name for the category of application they are using is "browser" and all the technical functioning of the browser and how the internet works, can be said in normal English usage to know what a browser is - it is one of a class of applications that they use to go on the web.
They click on an icon, a window opens up they go on the internet. The "browser"