What are Mutators and Accessors in Laravel

I am trying to understand accessors & mutators and why I need them. And my another ask is the middle part of an attribute's method for an example:

Accessor:

public function getFirstNameAttribute($value)
{
   return ucfirst($value);
}

Mutator:

public function setFirstNameAttribute($value)
{
    $this->attributes['first_name'] = strtolower($value);
}

Here, we can see getFirstNameAttribute and setFirstNameAttribute methods and I haven't been able to clear the middle part FirstName of them. I will really be grateful for a better explanation and kind cooperation.

Accessors create a "fake" attribute on the object which you can access as if it were a database column. So if your person has first_name and last_name attributes, you could write:

public function getFullNameAttribute()
{
  return $this->first_name . " " . $this->last_name;
}

Then you can call $user->full_name and it will return the accessor. It converts the function name into a snake_case attribute, so getFooBarBazAttribute function would be accessible through $user->foo_bar_baz.

Mutator is a way to change data when it is set, so if you want all your emails in your database to be lowercase only, you could do:

public function setEmailAttribute($value)
{
  $this->attributes['email'] = strtolower($value);
}

Then if you did $user->email = "EMAIL@GMAIL.com"; $user->save(); in the database it would set email@gmail.com