To attempt something is to actually try. You can attempt to do something you intended to do. To intend is more like you're thinking about doing something but not actually doing it at the time. It's like you plan to do it, but when you attempt something you are actually doing it. Making an attempt is physically doing it, intending to do something is thinking about doing it.

둘이 "뭔가를 하려고 한다'"는 뜻이라서 의미가 겹쳐지긴 하는데 차이가 있어요. 'to intend'는 '의도'의 뜻이 제일 포함되어 있고 (an intention = 의도) 'to attempt'는 '시도'의 뜻이 제일 포함되어 있습니다. (an attempt = 시도) 사실 후자는 'to try'의 완벽히 적당한 동의어예요. ^^

Gary has explained it above. Just to give you a few examples: I attempted the test several times. I attempted the survey yesterday but the link didn't work. I'll attempt the quiz tomorrow. I intend to go to the party. I intended to meet her, but something came up in the last minute. In colloquial English (at least in Australia), attempt is used as a verb only in the context of a quiz or exam or task. Otherwise, you would use the verb 'to try'. Eg. You should try this dish. Can I try using the keyboard? Otherwise, attempt is often used as a noun. Eg. Students have two attempts at this task. He made several attempts to charm her. Similarly, it is common for people to say: I'm thinking to go, or I'm thinking of going, rather than I intend to go. That said, I intend to go is fine.