What does it mean, Spark persist call on its own does not force evaluation.?

[#1]

I was recollecing few information about spark in documentation and crossed the below point

" Spark persist call on its own does not force evaluation.?"

[#2 · Accepted solution]

If you call persist() on an RDD, it means that the data in the RDD will be persisted but only later when something causes it to be computed for the first time. It is not immediately evaluated.