If someone is willing to do something, they are fairly happy about doing it and will do it if they are asked or required to do it. 乐意的
adjective [原级]愿意的,乐意的;乐于相助的,积极肯干的;出于自愿的,志愿的
Willing is used to describe someone who does something fairly enthusiastically and because they want to do it rather than because they are forced to do it. 心甘情愿的