ANCOVA stands for "Analysis of Covariance", it's a statistical technique that is used to compare the means of two or more groups while controlling for the effects of one or more additional variables.
For example, imagine that you are interested in the effect of a new teaching method on students' test scores. You randomly assign students to either a control group or an experimental group, and then measure their test scores. However, you also know that students' initial test scores (before the new teaching method is applied) might influence their final test scores. So, you want to control for the effect of initial test scores on final test scores when you compare the means of the two groups.
In this case, you would use ANCOVA to compare the means of the two groups while controlling for the effect of initial test scores on final test scores. The initial test scores would be used as a covariate in the analysis. By including the initial test scores as a covariate, ANCOVA allows you to adjust for any differences in initial test scores between the groups, and thus isolate the effect of the new teaching method on final test scores.
In simple terms, ANCOVA is a statistical method that allows to control for one or more additional variables when comparing means of two or more groups and help to analyze the relationship between the variables and the outcome.