Once you’ve been learning Mandarin for a while, you’ll probably start to notice that the particle 吧 (ba) crops up all over the place. It’s extremely common in everyday speech. 吧 has two main uses. The first is to mark and soften commands, requests and suggestions. Remember that 吧 doesn’t just indicate that something is a command or suggestion - it also makes it sound a little bit softer. This use of the 吧 sentence particle can turn a slightly pushy instruction into a more neutral one. The second main use of 吧 is as a tag question to ask for agreement or confirmation with what is being said. These aren’t ‘true’ questions - they’re just prompting the listener to agree. The speaker thinks that what they are saying is probably true, but they’d like to confirm it. 他姓王，对吧？ Tā xìng wáng, duì ba? His surname is Wang, isn't it?
I saw that you are learning Japanese. Is it comparable to 'ね' particle in Japanese? Like you said that these aren't 'true' questions.
The tip for 吧 is "word used when asking", which is a very strange description. It is used for suggestions and is comparable to '!'.
From Wiktionary: 1, used to indicate a suggested action: why don't you ... 2, express imperative mood: "let's go!" 3, indicate speculation: 门还没锁吧。Mén hái méi suǒ ba. The door has not been locked, I guess.
The concept here is rather "to leave (from the place where one is)". In English the way of expression is "to go".
When there is a danger, we warn people 走！ 快走！ ; In English it would be Run! Run quickly!
When we want someone to go to a place, we would say 去！快去！; In English it would be Go! Go there quickly!