Okay, but what does that mean? What does it mean to say “every aspect of life is considered part of the political system?”
In practice?
There is only one political party, the totalitarian's party. All other parties or movements are terrorists, wrongthinkers, or otherwise illegal and, fairly quickly, shot or imprisoned. They share this with authoritarians but the resemblance stops here.
There is only one business, the party's business. All businesses are controlled by the party, the economy is expected to do as they command, and when it doesn't the poor dupes running the factories are typically shot or at least arrested/sacked. Starting up your own business is illegal as you do the job the party assigns you.
There is only one opinion, the party's opinion. Disagreeing with the party in
any way gets you shot/imprisoned, but in the extreme case of totalitarianism having an opinion the party hasn't vetted ahead of time
also is thoughtcrime. In practice this means that art is only produced if the party agrees with the message of the art and anything else is obscenity, music is only written if the party agrees with it's lyrics (and possibly style, they may decide to outlaw, say, rock and roll simply because a high party member doesn't like the sound of it regardless of lyrics) and anything else is treason, movies are only produced if the themes are approved by the party and anything else is banned.
Totalitarian states normally pay lip service to science but only party-approved science is allowed to have any funding and their ideas on what should be allowed to be researched is based on ideology rather than reality, so their science tends to actually suck rather hard.
In practice there is no
truly totalitarian state just as there can be no perfectly communist, anarchist, or democratic state. The primary difference between totalitarianism and authoritarianism is that authoritarianism demands obedience but is generally not concerned with social habits while totalitarians invade as many aspects of daily life as they can manage. An authoritarian state will only have one party and stamp out any other political movement, but will not care who you marry and let you start your own business. Totalitarians want to control
all aspects of culture, art, and science.
Put more simply authoritarians want to be the only ones with guns. Totalitarians also don't want any guns in TV, books, or movies and will have parents arrested for their kids playing with an L-shaped stick because it might encourage thoughts of guns.