Farther and further are two words in the English language that are often confused and used interchangeably. Although they are related, they are not the same words, and they do not mean the same thing.
Farther is an adjective used to describe physical distance. For example, your house is farther away from the store than mine is. Further is an adverb used to describe an additional amount of time, distance, or degree. For example, I need to research this topic further before I can make a decision.
Farther implies a larger physical distance between two places, while further implies an additional amount of some kind. Therefore, you can use farther if you are talking about how two physical locations are far apart. You can use further to talk about an additional amount of something, such as difficulty, time, or distance.
Further can also be used metaphorically. For example, if you are trying to make a decision, you can say that you need to take it further. This means that you need to think about the decision in more depth. You can also use further to talk about a process that is taking a long time, such as a legal dispute that is dragging on.
In conclusion, farther and further are two words that are related but have different meanings. Farther is used to describe physical distance, while further is used to describe an additional amount of something or metaphorically to talk about processes or decisions that need to be taken further.