They're very nearly identical. Both refer to something of value not being used as desired. However, "waste" can be accidental or even unavoidable. If you're building a table and one of your boards is a little too long, the part you cut off can be called waste. If you destroy a board out of clumsiness, and have to discard it, that is also waste. "Squander" is a result of foolishness or bad judgment. If you used a very expensive wood for a work table instead of using that wood for fine furniture, that would be squandering that expensive wood.

no difference. "waste" is more commonly used, and has the meaning of 浪費, "squander" also means 浪費 is usually used for resources or money only. （亂花錢 = squander money, waste money)