Answer:
See Explanation
Step-by-step explanation:
I'll assume the question is about the use of constants in QBasic because consonants do not have any special function or usage in QBasic.
In simple terms: In QBasic, constants are used to represent elements that do not change in value during program execution.
Take for instance, you intend to use
in your program.
Its value is

So, 3.142 will always be a constant in your program. One of the ways it can be used in a program is:
10 LET PI = 3.142
The above represents a numeric constant. QBasic also have string constants.