factor what dose that mean????

A factor is something that you can divide byand get a 'whole' answer - nothing left over.

For example

The factors of  6 are 1,2,3 and 6

The factors of  3x+9 are 1, 3x+9, 3 and x+3

This is because 1*(3x+9) = 3x+9

and  3(x+3) = 3x+9

If you were ased to factorise 3x+9 the answer would just be 3(x+3)

so in algebra, if you are asked to factorise.  It means put brackets in.

Does that make sense?