SharePoint server provides the following validations in Out of the Box. Items cannot be saved until these validation criteria are met and custom messages, which can be set for specific validation failure cases, are displayed to the user.
Go to the sharepoint list and click on list settings, Here We can find under general setting Validation settings option will be there, Click on that.
Here we have to give our condition to a particular column, I given my condition like that column should take more than 20 words , And we can provide error message also .
Now we will check our condition
There is another way to create a Required column as shown.
Go to Create column option
Here we have one option called required that this column contains information, By default this is selected as No , We have enable yes.