Rich means having lots of money, or other items of value. It can mean splendid, costly or elaborate eg richly decorated or patterned. Alternatively it's used to describe abundance. eg My mind contains a rich supply of story ideas.
Soil which is rich contains plenty of nutrients and is very fertile. Richness in our own food comes from fat or spices. Engines can have too rich a fuel and air mix.
Sounds, scents and colours are often described as rich when they're heavy, full or deep.
The phrase that's rich is sometimes used to convey the idea something is considered outrageous, ludicrous or extremely amusing.
Do you have any riches?