Table index fields are important or not?

hi there

On the phpmyadmin tool, when is about adding a new field, you have the option to choose the place of tat field in your table. Seeing this, i got a question in my mind: Te order of the fields in a table, is important? Indexe fields have to be at the begining of the table or something like that?

If this is a rule to follow, this will affect speed of the interogations or it is about good practices only?

Also, is there any fields order rule to follow when I specify the conditions on WHERE part of the query?

no, and no

the only columns (not fields) that should be indexed are those which are used in queries for searching or joining