“Confidence level” in both calculators is expressed as a percentage and refers to the degree of confidence. One way to think of it is that if you were to hypothetically run the test (survey) 100 times with similar respondents at the 95% confidence level, 95 out of those 100 times you would obtain the same results within the confidence interval. For social science market research, a 95% confidence level is sufficient.
As noted in these calculators, you do not need to enter the population size being tested unless your sample will be over 1% of that population, in which case the margin of error calculation will improve depending on the population size. So, if you were planning to survey 50 CFOs of the Fortune 500 companies (10%), your margin of error will be +/- 13.16 points at the 95% confidence level, slightly better than a survey of 50 CFOs of the top 10,000 companies (0.5%), where the margin of error will be +/- 13.86 points at the 95% confidence level.