An error cause the correct behavior of software and affect the accuracy. It affect the expected result of application which might because of incorrect requirements implementation or because of invalid data entry by user.

Basic Type of errors :

1. Functional Errors: Let's take a example to make it very clear. Suppose you have a Pagination in the web page to display the listing, we have First     Page button and last page button that will take you to the First     page or last page with in the web page. While testing it when tester click the Last button, as expected it took him to last page but     actually on clicking that button user navigate to the second page,  which is an incorrect behavior as per requirements. That cause functional error in the software.
    
2. Communication Errors: Communication Errors occur for End-user did not get what he  want. Like if user is in “MENU” bar of the program and try to open the new file. But while user try to open the New file     the Program is getting closed. This Scenario make a communication gap between user and software. User didn't get what he want.
    
3. Missing command errors: Whenever the command for particular control is missing and user get stuck with in software while working that time command errors occur. Most common example is when application does not have a exit button.
    
4. Control Flow Errors: Any breaking in the flow of the application cause the error. For example Consider     the flow social media site when user send the friend request and has to accept it to add that person in his/her profile. Now in second scenario if user cancel the request that means that user should not add the profile. What if user get added to profile even if request is canceled. That kind of error comes in the     control flow error.
    
5. Calculation Error: The Calculation error is the basic type of error which as caused by incorrect logic used, incorrect code, math big calculation does not considered , etc.