What is data validation? (in a simple definition)

Verify data, something like this

var username = document.getElementById("input1").value

var password = document.getElementById("input2").value

// this is the validation:
if ( username == "anime" && password == "Anime132" ){
alert("Correct login data");
} else {
alert("Wrong login data");
}

Data validation is a process that ensures the delivery of clean and clear data to the programs, applications and services using it.
(For a simple definition.)

It checks for the integrity and validity of data that is being inputted to different software and its components. Data validation ensures that the data complies with the requirements and quality benchmarks.
(Add this on if you want it longer.)

Company has asked employees for suggestions on ways to personalize the retail customer's shopping experience. they want to supplement traditional appeals to the customer. you have come up with several ideas. select the idea or ideas you have decided to submit.c. designate two of the curtained areas in the women's dressing room for nursing mothers  d. tailor merchandise in each store to the preferences of customers in that geographical region