1. variable: a variable refers to the memory space used to store data. In Arduino programming, variables can be used to store different types of data, such as numbers, characters and text. When you declare a variable, you need to specify its type and name. For example, you can declare an integer variable intnum to store integers.

2. Function: A function refers to a code block that completes a specific task. In Arduino programming, functions can be used to encapsulate and organize code, which makes the program clearer and easier to maintain. Arduino programming language has provided many commonly used functions, such as digitalRead (), digitalWrite (), analogRead (), analogWrite () and so on. In addition, users can define their own functions to complete their specific tasks.

3. Statement: A statement refers to an instruction to complete a specific operation. In Arduino programming, commonly used statements include assignment statement, conditional statement, loop statement and so on. For example, you can use assignment statements to assign values to variables, or use conditional statements to perform different operations according to a certain condition, or use loop statements to repeatedly perform an operation.