when designing tables(and posts within it) using MySQL gui clients there's a area known as 'length' of the column. Just what will it mean. Is not range for any datatype (say)int fixed. Does length connect with the plethora of column value in anyway? Thanks.

yes, indeed. E.g. a varchar(255) area can support 255 figures.

see http://dev.mysql.com/doc/refman/5.0/en/data-types.html for those datatypes

Is not range for any datatype (say)int fixed.

No - but MySQL has some predefined sizes for integers.

Does length connect with the plethora of column value in anyway

Yes, it sets a restriction on how big what you devote there - try not to assume its directly equal to the amount of figures you type in (see previous link, also, that one on multibyte characters)