Adblock will block ads from web pages and mobile apps. Due to how internet domain names are designed, this block is not always perfect.
Firewalla Adblock utilizes well known DNS services to block ads from showing. When this is activated, it may take a while to be active. Windows/Mac/iPhone/Android all cache DNS entries, for example, to flush DNS cache on the iPhone is simply put the phone is airplane mode then turn it off.
Some websites will detect adblocking and prevent the content from getting served. If you encounter issues, you should turn off ad blocking.