Javascript comprises the muscles and sensory neurons of the body of a webpage, while html is the skeleton and css is the skin.
Control flow example: you're having a shower and you don't want to dry out your hair. If you used shampoo recently, you don't want to use it again this time, if it's been a few days you want to use it to keep your scalp clean.
You might represent this in psudo code like this: if daysSinceShower > 2: useShampoo()
A loop like just like repeating a task. If you need to make a series of cakes, following the steps in the recipe is like an iteration of the loop
The DOM - document object model - is an abstraction of a webpages contents that has a structure and can be manipulated with Javascript. You might interact with the DOM by making it so when a user presses a button a message appears and some text changes colour.
Accessing data from arrays uses an index (a number), whereas an object involves using a given 'key', which is typically a string, and has an associate 'value'. These pair is called a key-pair value.
Functions are a series of actions you want to repeat. They're incredibly useful for cutting down code in a codebase, making simple changes across a document in many places and also help reduce the risk of uncaught bugs from if code has instead been copied and pasted and one or more instances of the code haven't been updated and/or patched.