factorizing of algebric expressions is like "splitting" an expression into a multiplication of simpler expressions.
factor = 2y+6
Both 2y and 6 have a common factor of 2
2y is 2 × y6 is 2 × 3so you can factor the whole expression into
2y+6 = 2(y+3)
So 2y+6 has been "factored into" 2 and y+3