This adjective phrase is used to describe a situation where there is a great deal to be won…or lost. For instance, a HIGH STAKES poker game is one where the players are betting a whole lot of money. There is great risk, but there is also a chance for a greater reward.
We might use these words in a slightly different way to convey the same meaning. Pretend, for example, that I am meeting my girlfriend’s father for the first time at dinner tonight. I love my girlfriend and hope to marry her someday, and I’ve been told that she will never marry anyone her father does not like.
I might say that the STAKES will be very HIGH at tonight’s dinner.