How Expressions Trees are different from Lambda Expression?

A common misunderstanding is that expression trees are identical to lambda expressions. But this is not true since you can also create and modify expression trees by using API methods i.e. without using lambda expression syntax at all.
Also, every lambda expression cannot be implicitly converted into an expression tree. Only expression lambda is implicitly converted an expression tree and statement lambda i.e. multi-line lambda cannot be implicitly converted into expression tree.