Merge pull request #11 from pBouillon/fix-typos-in-chapter-4

Fix minor typos in chapter 4

Author: Armenvardanyan95

docs/chapter-4.md

@@ -13,11 +13,11 @@ As mentioned in the previous chapter, we need a state management solution that i
 
 ### How do bugs happen?
 
-In most cases, we have bugs not because the code is wrong (in that case we essentially didn't tell the computer what _exactly_ we wanted), but because the data is not in the expected state. The variable `age` all of a sudden holds a negative value, because someone misclicked when the IDE offered an autocomplete or a correction. Or maybe the Array of users is empty, because we called the wrong API, or stored the data in the wrong variable, or forgot to subscribe. Problems like this happen _all the time_. Remember the last vry annoying bug you encountered. Was it because of a very minor mistake like a typo? If yes, answer the following: how frustrating was the whole experience?
+In most cases, we have bugs not because the code is wrong (in that case we essentially didn't tell the computer what _exactly_ we wanted), but because the data is not in the expected state. The variable `age` all of a sudden holds a negative value, because someone misclicked when the IDE offered an autocomplete or a correction. Or maybe the Array of users is empty, because we called the wrong API, or stored the data in the wrong variable, or forgot to subscribe. Problems like this happen _all the time_. Remember the last very annoying bug you encountered. Was it because of a very minor mistake like a typo? If yes, answer the following: how frustrating was the whole experience?
 
 ## What does NgRx offer?
 
-NgRx, as mentioned, is built on concepts of Redux. It utilizes core ideas like `Stores` (the place where the application states is stored), `Actions` (events that notify the `Store` that some change to the state is to happen), `Reducers` (functions that determine how a certain `Action` affects the `State`), and also adds concepts like `Selectors` (functions that allow to pick a slice of the `State` as an `Observable`) and `Effects` (special functions that work on side effects like data loading and API calls). It also provides utility functions to make writing boilerplate code easier and even utility libraries like `@ngrx/entity` to work with large lists of data. We will learn in depth about all of those concepts and tools in corresponding chapters.
+NgRx, as mentioned, is built on concepts of Redux. It utilizes core ideas like `Stores` (the place where the application states are stored), `Actions` (events that notify the `Store` that some change to the state is to happen), `Reducers` (functions that determine how a certain `Action` affects the `State`), and also adds concepts like `Selectors` (functions that allow to pick a slice of the `State` as an `Observable`) and `Effects` (special functions that work on side effects like data loading and API calls). It also provides utility functions to make writing boilerplate code easier and even utility libraries like `@ngrx/entity` to work with large lists of data. We will learn in depth about all of those concepts and tools in corresponding chapters.
 
 Together, this tools allow us to build a truly scalable state management solution.