Underlying trend rate of growth

I remember there was a question about it somewhere (AQA exam board), it mentioned the underlying trend rate of growth and trend rate of growth or just growth. I can't seem to find anywhere what an underlying trend rate of growth it. Someone care to explain please?

Thank you.

So, if you look at actual growth as the actual level of growth each quarter, the underlying trend rate of growth is kinda like the average... So, whilst the actual level will fluctuate a fair bit, the underlying trend rate of growth is kinda like the average.

If you look at this image here, the curved line is actual growth, the straight line with a slight positive gradient is the underlying trend rate of growth!