The Four of Swords signifies Air (information, ideas, intellect) related to the element Earth (material things, foundations, building and fortifying). It points to the realm of tinkering, of collecting, of breaking things down and putting them together— figuring out how they work. Perhaps it represents a hobby, perhaps it represents a journey toward comprehensive knowledge, or perhaps it represents fixing broken things.
This is a card that may point to one or more of a person's hobbies, or hint at something that needs to be fixed, or to problems that have been solved. If it points to anything that needs fixing then it is probably the case that the knowledge, or the tools to fix it are readily available.
If it indicates a relationship, this card could indicate an unhealthy dynamic in which one partner (or both!) feel the relationship is dependent upon them fixing the other.
The Abstract Four of Swords represents abstract Air phenomena (knowing, certainty or doubt) which pertain to the element Earth (pragmatism, fundamentals, basics, material security). It signifies practical discernment, or perhaps intellectual constraint.
The practical discernment represented by this card is careful assessment of the mundane sphere of life, of things like food and finances, business and social obligations. The Abstract Four of Swords signifies the mindset which is partial to methods which are known to work, very decisive, and wary of fanciful new ideas which may serve as distractions, kind of the opposite of having one's head in the clouds.
Intellectual constraint, on the other hand, may prevent one from coming to a more helpful understanding of their situation. Limits on knowledge may be natural or artificial, meaning that a person may have hit a limit on what they are capable of understanding, or some other force could be preventing them from studying further— say an emotional block, or contradictory teachings from any number of institutions.