The meanings overlap. The shades of meaning are imprecise. I suggest using "normal" if you are not sure which to use. "Normal" suggests something that is merely common, popular, or customary. "Standard" carries a sense of something formalized, specific, possibly written, with a sense of "should" or "ought" behind them. And it carries a sense of being a measuring stick, something that you can compare something else to. As an example of "normal," I can imagine a conversation between teenagers: "I like to put ketchup on scrambled eggs." "That's not normal!" "Is it illegal?" "No." "Is it immoral?" "No." "What's wrong with it?" "It's just not normal. Normal people don't do that." "Well, it's normal in MY family." As an example of "standard," I can imagine this conversation: "I ordered a hamburger without pickles. It took twenty minutes, it was cold, and it had pickles on it. That isn't up to your standards!" "What standards are those?" "The ones framed, there on the wall! The "Burgerland Credo and Customer's Bill of Rights." 'We cook fresh hamburgers to order and serve them hot in ten minutes or less.'"

They have almost the same meaning, however they are used in different situations. Standard means a level of quality, or something that is used as a measure, worth, etc. Example: The standard of work is very good. The standard measure of lenght is meter. Normal means usual, common, conforming to a standard. Example: It's normal to feel sad sometimes. The temperature is below normal. Normal is more common. Standard is usually used in science, or bussines, etc. I hope this helps.