The terminology for comparing apples with apples in the financial world. Comparing year on year financial performance means that data must be truly comparable. Data that distorts true comparison is eliminated or introduced in order to facilitate easy comparison of underlying performance.
A business is steadily producing $1 Million every year in profit. Then another business is acquired that also produces $1 Million a year in profit. Headlines after one year could say 'Business profitability doubles in 12 months !' That is a true statement, but only because another business was bought. If we were comparing 'like for like' we would have to say that the performance of the original (last year) business is actually unchanged.