In addition to the above basic usage, when has some other usages and collocations. For example, "every time" means "whenever ..."; "Since when" means "since when"; "Until when" means "Until when" and so on. In addition, there is a common phrase, which means "speaking of, involving", which is used to lead to a topic or theme, usually used in spoken English. For example, "When it comes to cooking, I prefer Italian food" means "When it comes to cooking, I like Italian food". In short, when is a commonly used conjunction, and mastering its basic usage and common collocation is very helpful for learning English.
When, when ...