What is the importance of a proposal?

Which one?

pro·pos·al
prəˈpōzəl/Submit
noun

1. a plan or suggestion, especially a formal or written one, put forward for consideration or discussion by others.
"a set of proposals for a major new high-speed rail link"

synonyms: plan, idea, scheme, project, program, manifesto, motion, proposition, suggestion, action point, submission, trial balloon
"the proposal was rejected"

2. an offer of marriage.