access modifiers in c#

I think the best bet for you is to pick up a good book and then read about modifiers.
These would be described in detail in the initial chapters.

public member:public member can be accessible any where in the project as well as other project also.

private member :private member can be accessible anywhere within a class itself not outside from that class.

Internal member: Internal member can b accessible anywhere whithin a project.

protected member :protected member can be accessible within a class where member declare as well as derrived class also.

protected internal : protected internal member enjoy dual effect.it is accessible anywhere in the prject as well as if that class is inherite one other class and that is in other project then only it can be accessible to other project also.

This might help full for you
http://www.dotnetbull.com/2013/10/public-protected-private-internal-access-modifier-in-c.html [^]

Accessibility of access modifies in c#

Access Modifiers	Inside Assembly		Outside Assembly
	With Inheritance	With Type	With Inheritance	With Type
Public	ü	ü	ü	ü
Private	X	X	X	X
Protected	ü	X	ü	X
Internal	ü	ü	X	X
Protected Internal	ü	ü	ü	X

Reference :-
dotnetbull - what is access modifier in c#

The big two are public and private and all they do is say how much of you class can be seen by the outside world.
Anything you declare as private can only be accessed within the class itself:

public class MyClass
   {
   private void myFunction(){}
   ...
   myFunction();   // LEGAL, no problem
   ...
   }
...
   MyClass mc = new MyClass();
   mc.MyFunction();   // ILLEGAL - no access

Anything you declare as public can be accessed by any code anywhere.

The others fall in the middle of these two:
protected means that it is only available within the class, and in any class derived from the class. It's private but with special access given to derived classes.

internal means public to classes within the same assembly, and private to classes outside teh assembly. So if you build your own DLL, all your classes in side the DLL can access the objects, but classes which reference your DLL cannot see them.

protected internal is a combination of protected and internal - they are visible within the assembly exactly like internal objects, but they are also visible to derived classes outside, the same as protected

Is Google broken at your place. Being a freshers doesn't mean you complile list of questions at CP and wait for cooked answer. You should look for these answers yourself.

This can be a good start for you:

Access Modifiers (C# Reference)[^]

Private members are available only within the containing type, where as public members are available anywhere,there is no restriction.
Protected members are available within the containing type and to the type that derives from the containing type.

Internal is available anywhere within the containing assembly.It is a compile time error to access an internal member from outside the containing assembly
Protected Internal can be accessed by any code in the assembly in which it is declared or from within a derived class in another assembly.It is a combination of internal and protected access modifier.
Assembly in .NET is generated if you compile a project.Assembly is of 2 types-executable and .dll. Console, windows applications generate .exe assembly whereas library and asp.net generate .dll assembly.
Assembly is intermediate code langauge.

http://www.samplecoder.com/2014/11/public-private-protected-internal-and.html[^]