I tried to connect to a hc-05 with the popular way on the Internet but kept getting an error(503) of mac address not found, I then found this block of code that works but don't understand how,.
Here are several links to articles that explain 'how things work'
The resources to help you learn how to use the AI2 tools and explain what various components do. A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook App Inventor 2 Book: Create Your Own Android Apps ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.