What language / locale are you from? It makes a difference as to what is called what. Keyboard terms have been a little different from company to company, system to system, but they have somewhat standardised over time. So the "correct" terms are:
Space or Spacebar: pretty obvious, it makes a space.
Backspace: It removes the previous character and moves the cursor BACK one SPACE.
Delete: It deletes the character in the cursor position without moving the cursor.
Windows key: This is only called the Win key on boards that have it labeled as such. The more universal terms are OS, Super, Meta and GUI, but since it was first introduced by Microsoft, they named it first and it sort of stuck, despite not being meaningful on other systems.
Enter: Used for when you have completed an entry and wish to ENTER it into the system. Return is still sometimes seen (usually on retro style keycap sets wishing to emulate terminal boards, but Enter is the more modern and accurate term) and refers to Carriage RETURN from typewriters which returns the cursor to the beginning of the line.
Using the most universally accepted terms gives you the highest chance of being understood by the largest number of people when talking about keyboards.
