This tutorial has covered a lot of material and it would be worth going through at least a couple more times. If some of the concepts still seem a little abstract just keep trying to relate them back to word search experiment.
Please bear in mind that the tutorial only covers simple experiments where you only have 2 conditions i.e. the experimental group and the control group and where you only have one independent variable and one dependent variable. Experiments can be more complex than this you can have more than two conditions and you can have multiple independent and dependent variables but the logic remains the same.
Finally I'd like to conclude with a definition of an experiment because having completed the tutorial it should make more sense.An experiment is a study of cause and effect. It differs from simple observation in that it involves deliberate manipulation of one variable (the independent variable), while controlling other variables (extraneous variables) so that they do not affect the outcome, in order to discover the effect on another variable (the dependent variable) S. Heyes (1986).