Row numbering

Hello!

I would like to ask if there is any easy way for numbering of rows. I am not sure if I am writing it right, let me explain. In the column there will be number of rows: 1, 2, 3… and if I sort the table by different column, these numbering will stay 1, 2, 3. Do you know what I mean? I cant see how to make this, please, help if you can ??