Ideal time (or ideal development time of effort) is the amount of time it will take you to finish a task if you had no interruptions or impediments. It is an estimate of size or effort and has little to do with time, since you rarely ever get contiguous blocks of productive time.
Estimating in ideal time is affected by various factors like the developers own cognitive biases, their skill and experience levels, complexity of the problem, the design of the software, and available tools, to name just a few.
Ideal time can be used to derive an estimate of duration.
Estimating in Ideal Time might not be ideal