Idioms are a unique part of language. For someone learning an idiom, the phrase may very well have little to no literal meaning, but it's through one's exposure to cultural and social norms that one begins to understand what is really being said. Or, as the dictionary defines idiom, "a group of words established by usage as having a meaning not deducible from those of the individual words."
"thinking outside the box."
For example, "to think outside the box." What does this even mean? For many learning English this idiom can be confusing, disjointed, and vague. In essence, though, it simply means to think in a way that might not seem normal, logical, or straightforward. For a practical illustration, let's look at the picture below. We see that there are nine dots.
Your goal, dear reader, is to draw a continuous line that will cover all of the dots. You cannot go over the same dot twice. Can you do it?
(Think outside the box.)
Here are some things that you might have tried.
#1. Though this is four lines and it does cover all the dots, the red line shows that you overlapped the center dot twice, therefore making this answer invalid.
#2. Here in number two we see that one of the dots on the outside is not covered.
#3. Here we see that the dot in the middle is not covered.
But perhaps you were able to do it. Does it look anything like this?
Here you start at the bottom right with the purple line, then to the top left blue line and head down, then go from the bottom left following the red line, and then from the top right cover the last two dots as is seen with the green. You've done it!
"The early bird gets the worm."
Another very common idiom used by English speakers is "The early bird gets the worm." Let's talk about nature for this one. In the morning, worms are known to make their way to the surface to do who knows what. It's at this time that birds are able to help themselves to a nutritious breakfast. Imagine if you were a bird and you slept in. You wake up 10 minutes later than everyone else and everyone is done and all the worms have been eaten. Now you are hungry.
Being that this phrase is often said from one person to another, the phrase, in essence, is talking about the idea that arriving or being some place early has many benefits. People might say this idiom when they go someplace early and get some special merchandise that would have been sold out if they'd arrived later.
Talking about food stuff, another one you might hear is the following.
"My plate is full."
Perhaps this originated when someone had too much food on their plate and it became impossible for them to add any more. This idiom often refers to the times when you have too many things to do and can't add anything else to your to do list.
Anyway I hope that these are helpful and insightful. Next time let's look at some English proverbs.