The five are usually listed and less often examined as a system. What they have in common is that four of them are actions with public and measurable form, and the fifth is a sentence.
The shahada is the only one that is purely verbal, and it functions as the point of entry: saying it sincerely before witnesses makes a person Muslim. There is no ritual of initiation, no officiant required and no institution to join, which is a genuinely distinctive feature among the large religions and goes some way to explaining the speed of Islamic expansion in its first centuries.
The other four distribute obligation across every timescale a human life has. Salat structures the day, zakat the year, sawm the calendar month of Ramadan, and hajj a lifetime. That is a tidier arrangement than most traditions manage, and it is one reason the framework is taught to children as a structure rather than as a list of duties.
Three of the five are also collective by design. Friday prayer requires a congregation and cannot be performed alone. Ramadan is kept simultaneously by everyone in a community, which visibly reshapes the working day, the restaurant trade and the broadcast schedule in Muslim-majority countries. The hajj assembles people from every country in identical unsewn cloth in the same place in the same week, and its levelling function, the same two garments on the wealthy and the poor, is stated explicitly in the tradition rather than inferred by observers.
Zakat is the one with a number in it, which makes compliance auditable in a way piety usually is not. Hajj is the one with a condition: it is owed only by those with the physical and financial means, and borrowing in order to perform it is discouraged.