What are HTTP requests?
HTTP requests are basically requests between a client and server. These requests are used to access and manipulate data on the backend. For example, two common HTTP requests are GET and POST. GET requests data, POST sends data.
What is the difference between Array#map and Array#each?
Array#map returns a new array with the values returned by the block, but it does not affect the original array. Array#each iterates over each item in an array, updating the value with the value returned by the block.
What important information does a derivative tell us about a function?
A derivative is the slope of a function.