If something's probably true, it's likely. When you walk in the rain, it's likely that your shoes will get wet.
Likely is an adjective that's perfect for describing things you can imagine happening, such as the likely destination of next summer's vacation. Any time that something is in the cards, or bound to happen, you can explain that it's likely to happen. Though it's rarely used this way today in American English, one meaning of likely since the 15th century has been "good looking or attractive."