Important / Unimportant means that you can completely disregard the validity and credibility of what I say. But it is more than that – Important / Unimportant means that you can disregard my efforts’ worth, discredit the value of anything good that I’ve done and demean the things I’m bringing to the table as an equal participant.
Relevant / Irrelevant means that to invest any of your time in seeing or hearing about what I have created or the work I’ve done is a waste of your time in your estimation or in the estimation of those who are choosing what to offer you (whether news org. or manufacturer, investor or retailer.)
Value / No Value means that it is worth or not worth you giving any of your money for it – or anyone giving or not giving their money for it. Also that means it is worthy or not worthy of your support (or anyone’s support) of it.
Those three concepts are easy enough to understand from a dictionary. They are harder to understand in implications and in the applications of them made everyday in real life.