How exactly does grammarchecker show mistakes and how to correct them?

Here is a step by step guide on how to use grammarchecker.co. The first step is to type grammarchecker.co in the search browser’s navigation bar. The site will open and the screen will display a message telling you the types of documents that it can handle. It gives an option ‘Select File’; click on it and it will show folders and files on your desktop. Select the file that you want to run the check on and it will copy it directly into the display area. the other way of submitting text for checking is by selecting the text on your computer and copy/pasting it in the display window. Now at the bottom of the message area on the left is a blue button on which is written ‘American’ and there’s a small down arrow with it. if you want your document checked for the American style of writing, move your mouse over to the ‘Check Grammar' button and click. If you want grammarchecker.co to run the check in British, South African, Canadian, Australian or New Zealander dialect of English, click on the required button. Grammarchecker.co will load the selected country’s grammar and spelling rules. Click on ‘Check Grammar’ and the application will start checking the submitted document. Once it has finished checking the document you will see words in yellow and red and pink on the display window. The words appearing in red or pink indicate that the word has been spelt wrongly. Place the mouse over the word and click the left button of the mouse. The correct spelling will be displayed with an option to replace the original word. Now it’s the user’s choice to replace the word or not. The yellow words indicate grammar mistakes and when you place the cursor over them and press the left button, the system will explain the error and how to remove it. Now, again it’s the user’s choice to make the change or to ignore it. After completing the corrections you must select the text and copy/paste it where you want. This is how grammarchecker.co works.