Possibly the most fundamental notion in computer science is the definition, design, and implementation of how tasks are accomplished in a given functional area of a computer program. A straight forward term for this notion is Algorithm. If you take a look around as you move through an ordinary day you will see algorithms popping up all around you, even though, at first glance, they may not seem like algorithms.
For example, let's say you need to do a load of laundry. The sub tasks you perform to accomplish this task are collectively known as an algorithm. Another great example is a recipe for cooking your favorite meal. In both examples, you may not know how to do a load of laundry at first or cook a fancy meal from memory so you have to follow the instructions on the inside portion of the washing machine lid or a recipe from a cookbook.
Sooner or later, with practice, you will understand these algorithms well enough to not need the instructions. Furthermore, you may get to the point where you are embellishing the process by adding extra tasks to get to a better end result. Maybe adding fabric softener to a load of laundry or a new seasoning that wasn't in the original recipe but makes the meal taste better. You will also find, through experimentation, what works and what doesn't work. For instance, not separating colors from whites in the load of laundry may make the end result a little frustrating, even costly, or perhaps you put too much salt in your favorite recipe. Over time though, you learn how to use the sub tasks within the overall tasks efficiently to produce the expected results in predictable manner. This is the essence of an algorithm - sort of.