this is my server.js file with comments

server.js

@@ -1,74 +1,74 @@
-const express = require('express')
-const app = express()
-const MongoClient = require('mongodb').MongoClient
-const PORT = 2121
-require('dotenv').config()
+const express = require('express') // needed to get express working
+const app = express() // app now holds express() -- this acts like a method?
+const MongoClient = require('mongodb').MongoClient // gets database to connect
+const PORT = 2121 // this is the local port number
+require('dotenv').config() // this will require .env's configuration
 
-let db,
-    dbConnectionStr = process.env.DB_STRING,
-    dbName = 'todo'
+let db, // declaring db variable, this holds client.db(dbName)
+    dbConnectionStr = process.env.DB_STRING, // dbConnectionStr is holding the info that points to the .env file with the database string
+    dbName = 'todo' // 'todo' is the name of the database
 
-MongoClient.connect(dbConnectionStr, {useUnifiedTopology: true})
-    .then(client => {
-        console.log(`Hey, connected to ${dbName} database`)
-        db = client.db(dbName)
+MongoClient.connect(dbConnectionStr, {useUnifiedTopology: true}) // I think this is telling MongoClient.connect to use specific strings -- don't really know what useUnifiedTopology is
+    .then(client => { // stil trying to wrap around how then works
+        console.log(`Hey, connected to ${dbName} database`) // console logging so we can see what's happening 
+        db = client.db(dbName) // db is holding client.db(dbname)
     })
-    .catch(err =>{
-        console.log(err)
+    .catch(err =>{ // the catch is what's used in case the .then fails, yeah?
+        console.log(err) //shows us what err would be
     })
 
-app.set('view engine', 'ejs')
-app.use(express.static('public'))
-app.use(express.urlencoded({ extended: true }))
-app.use(express.json())
+app.set('view engine', 'ejs') // this tells app to looks at these two files?
+app.use(express.static('public')) // tells app to use express found in static?
+app.use(express.urlencoded({ extended: true })) // not sure what this does
+app.use(express.json()) // this parses express info into JSON
 
-app.get('/', async (req,res)=>{
-    const todoItems = await db.collection('todos').find().toArray()
-    const itemsLeft = await db.collection('todos').countDocuments({completed: false})
-    res.render('index.ejs', {zebra: todoItems, left: itemsLeft})
+app.get('/', async (req,res)=>{ // points to the '/' directory or folder but still not clear about async and how it works
+    const todoItems = await db.collection('todos').find().toArray() // todoItems is holding awais (which I'm not clear about really) while findind collections and adding them to an array
+    const itemsLeft = await db.collection('todos').countDocuments({completed: false})  // itemsLeft is holding awais (which I'm not clear about really) while findind collections and adding them to an array
+    res.render('index.ejs', {zebra: todoItems, left: itemsLeft}) // res.render... renders index.ejs to something readable
 })
 
-app.post('/createTodo', (req, res)=>{
-    db.collection('todos').insertOne({todo: req.body.todoItem, completed: false})
-    .then(result =>{
-        console.log('Todo has been added!')
-        res.redirect('/')
+app.post('/createTodo', (req, res)=>{ // post will post info on /createTodo
+    db.collection('todos').insertOne({todo: req.body.todoItem, completed: false}) //this adds info into the 'todos' collection 
+    .then(result =>{ // still not too clear about .then
+        console.log('Todo has been added!') // let's us see what happens
+        res.redirect('/') // this is going to redirect the response
     })
 })
 
-app.put('/markComplete', (req, res)=>{
-    db.collection('todos').updateOne({todo: req.body.rainbowUnicorn},{
-        $set: {
-            completed: true
+app.put('/markComplete', (req, res)=>{ // this put will move into to the markComplete folder
+    db.collection('todos').updateOne({todo: req.body.rainbowUnicorn},{ // this updates the 'todo's by one collection/input and sends it to... rainbowUnicorn?
+        $set: { // sets something for us?
+            completed: true // returns true if it's true?
         }
     })
-    .then(result =>{
-        console.log('Marked Complete')
-        res.json('Marked Complete')
+    .then(result =>{ // still not sure
+        console.log('Marked Complete') // let's us see what's going on
+        res.json('Marked Complete') // parses response into JSON
     })
 })
 
-app.put('/undo', (req, res)=>{
-    db.collection('todos').updateOne({todo: req.body.rainbowUnicorn},{
-        $set: {
-            completed: false
+app.put('/undo', (req, res)=>{ // puts info into /undo 
+    db.collection('todos').updateOne({todo: req.body.rainbowUnicorn},{ // accesses the collection 'todos' and updates it with one piece of info
+        $set: { // sets something for us?
+            completed: false // returns false if it's false?
         }
     })
-    .then(result =>{
-        console.log('Marked Complete')
-        res.json('Marked Complete')
+    .then(result =>{ // still not too clear about .then
+        console.log('Marked Complete') // let's us see what's going on
+        res.json('Marked Complete')  // parses response into JSON
     })
 })
 
-app.delete('/deleteTodo', (req, res)=>{
-    db.collection('todos').deleteOne({todo:req.body.rainbowUnicorn})
-    .then(result =>{
-        console.log('Deleted Todo')
-        res.json('Deleted It')
+app.delete('/deleteTodo', (req, res)=>{ // deletes info in the /deleteTodo
+    db.collection('todos').deleteOne({todo:req.body.rainbowUnicorn}) // deletes one item from the todos collection
+    .then(result =>{  // still not too clear about .then
+        console.log('Deleted Todo') // let's us see what's going on
+        res.json('Deleted It')  // parses response into JSON
     })
-    .catch( err => console.log(err))
+    .catch( err => console.log(err))  // let's us see what's going on
 })
 
-app.listen(process.env.PORT || PORT, ()=>{
-    console.log('Server is running, you better catch it!')
+app.listen(process.env.PORT || PORT, ()=>{ // sets up a listener to listen to a PORT that we declared earlier
+    console.log('Server is running, you better catch it!') // let's us see what's going on here
 })