The Latin word "Ceteris Paribus," often used in Economics simply means, with other things being the same or all things being equal.
The major reason why economics often use "Ceteris Paribus" is to eliminate other factors which might complicate an outcome.
For instance, If the price of pork increases, people will purchase less pork, that is Ceteris Parabus. In this instance, ceteris paribus means that the possibility of other factors affecting the sales of pork will not be considered. Other factors such as an announcement were made that pork causes cancer, or the price of Chicken has increased, thereby making pork the best alternative, hence, all these other factors will not be considered, therefore in this situation, economics only wants to consider what happens if the price of pork rises while keeping all other factors the same.