Here are some of the things you will use on a regular basis:

Anything contained in double quotation marks ( “ “ ) is a string.

Console.WriteLine(“ something here “);
	Prints the words something here onto the screen and moves the cursor to the next line

Console.Write(“ something here “);
	Prints the words something here onto the screen and leaves the cursor on the same line

Console.ReadLine( );
	Waits for the user to type something and hit the enter key.  This must be used in an assignment statement such as this
	string line = Console.ReadLine( );

To convert the string input into an actual number requires use of the Parse method.

string line = Console.ReadLine( );
int myValue = System.Int32.Parse(line);

string line = Console.ReadLine( );
double myValue = System.Double.Parse(line);

When you see this line:
Console.WriteLine(“Your average is {0}.”, avg);

You see that the {0} is a placeholder that will be filled with the value that is stored in avg.