The meaning of the word "variable" depends on the field where it's being used.
In programming, a variable is a particular piece of data that holds a value. Depending on the configuration, that value can change or remain fixed.
For instance, in JavaScript, you can implement a variable to change over time with the "var" and "let" keywords. But if you want, you can implement a variable so it doesn't change with the "const" keyword.
In this article, the kind of variable we’ll be looking at is not the one in programming but the one you'll deal with in research. Precisely, we’ll look at the differences between the two main types of variables in research – dependent and independent variables.
But before we look at the differences between dependent and independent variables, we need to understand what a variable is first.
What We'll Cover
 What is a Variable in Research?
 What are Dependent and Independent Variables?
 What are the Differences between Dependent and Independent Variables?
 How to Identify a Dependent Variable from an Independent Variable
 Conclusion
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What is a Variable in Research?
If you’re conducting research, you’ll be measuring a lot of values. So, in research, a variable is anything you’re trying to measure. It could be age, temperature, length, height, mass, weight, or any other thing that can have a value.
In addition, you’ll be measuring those variables in different units – centimeters (cm), meters (m), grams (g), kilograms (kg), and many more.
These units can’t be neglected, but as far as variables are concerned, whether dependent or independent, the values are what really matter.
What are Dependent and Independent Variables?
Dependent and independent variables depend on whether one variable determines the outcome of the other or not.
A dependent variable is a variable whose changes and its outcome depend on another variable. On almost all occasions, the variable the dependent variable depends on is an independent variable.
Dependent variables are also called the response or outcome variables because they represent the outcome of the values you're measuring. That is, what you record after manipulating the independent variables.
An independent variable is a variable whose outcome or changes do not depend on another variable. It is the exact opposite of the dependent variable, at least according to what the name implies.
Independent variables are also called predictor variables because you can use them to predict the outcome of a dependent variable. That is, when you manipulate independent variables, they can give you the outcome of a dependent variable.
What are the Differences between Dependent and Independent Variables?
Basis  Dependent Variable  Independent Variable 

Type  It is the "response" variable  It is the "effect" variable 
Outcome  Outcome depends on another variable (usually the independent variable)  Outcome does not depend on another variable 
Changes  This variable changes over time. Consider the dependent variable as a variable you declare with the "let" or "var" keyword in JavaScript. You can later change it.  This variable never changes. Consider the independent variable as the variable you declare with the "const" keyword in JavaScript. It is fixed unless you explicitly change the value. 
Manipulation  Dependent variables cannot be manipulated because their value depends on the independent variable.  Independent variables can be manipulated to determine the outcome of a dependent variable. 
Position on a Graph  Dependent variables are placed on the yaxis (vertical axis) on a graph  Independent variables are placed on the xaxis (horizontal axis) on a graph 
How to Identify a Dependent Variable from an Independent Variable
We've taken a look at what variables are, what dependent and independent variables are, and the exact differences between dependent and independent variables.
But how exactly would you differentiate a dependent variable from an independent variable? We are going to look at two experiments or examples:

how Vitamin A helps mothers produce milk

the level of light nocturnal insects (insects active at night) are attracted to
For the first experiment, the sources of vitamin A the mother takes in from foods like fish oil and green vegetables are the independent variable. That's because the researcher can change [decrease or increase] the amount given to the mothers. How the body of the mother responds in producing more milk is the dependent variable.
For the second experiment, the level of light is the independent variable because the researcher can change it. How nocturnal insects react to that level of light is the dependent variable.
Conclusion
In this article, you learned about the differences between dependent and independent variables. We looked at:

what a variable is in research

the two main types of variables (dependent and independent variables)

what dependent and independent variables are

and how to differentiate a dependent variable from an independent variable.
I hope this article gives you a knowledge of what research variables are and how to differentiate a dependent variable from an independent variable.
Thank you for reading.