This is a translation wikipedia sources on flu mechanisms. My attempt at being a science writer.
The virus is covered with sticky parts ("HA") which recognize certain sugars that your cells have on their outside surface. (Pigs etc have them too.) When the sticky parts recognize the sugar they change shape and harpoon your cell. This causes your cell to form a cavity around the virus because the virus is sticking to the cell membrane. Think tennis ball rolling on a sheet of velcro.
Some extra machinery the virus carried with it (M2) causes the virus jacket to fragment once insde. Then the virus's now-bared RNA codes are moved into the cell's nucleus by the cell.
In the nucleus the RNA are copied, and some are sent out of the nucleus to be turned into proteins. Some of the proteins go back to the nucleus, pick up the viral RNA and package it. The packages head out again, this time attracted by additional machinery (NEP etc) to a spot on the inside of the cell's membrane where other proteins are waiting. They all get assembled into a ready virus, and one final viral machine, "NA", cuts the sugars that might be holding the new virus (studded with HA after all) back.
Pretty clever, how it brings all those tools for each step, and of course how it exploits cellular machinery to move around the cell. Yet reassembles. And how it keeps its harpoon sheathed until it tastes that sugar that means prey.
A finely tuned mission-impossible subversion of an enemy factory. Conducted by nano drones.
Note that flu drugs work by interfering with NA.
Note that the flu A genetic code is RNA which is more succeptible to copying errors than DNA. Faster evolution.
