Center is a formatting element set text centered align, centered text aligned at middle of document.
<center>Content</center>
Or
<tag><center>Content</center></tag>
You can apply center element to any element and use any where within a HTML document.
Center is a pair tag and output of center element is centered text like you can see in above example.
Open notepad or any other text editor, follow the following points.
save file with name task.html or task.htm and then open it using any browser and see results.
Don't forget center is non empty element which means it always comes in pair.