A wise old man is a person (usually a man) who has lived a lot of years and has gained a lot of knowledge and experience from life. He has learned many things and can pass on his wisdom to others.
Think of it like this, imagine you have a grandpa or an uncle who has been around a really long time. They have seen and done many things in their lifetime, from surviving tough times to learning from successes and failures. This knowledge gets collected in his mind, making him wiser.
People often seek out the advice of a wise old man because they know he has a lot of experience and can provide useful information or advice. They are seen as a source of guidance or a mentor to help you make better decisions in life, like a teacher.
So, just like your grandfather, a wise old man is someone who has a lot of knowledge and experience that he can share with you to help you be more successful and make better decisions.