Here is an animation that is worth a watch. The screen is split into two parts.
On the left hand side we see how much CO2 there is in the atmosphere, measured day by day at different places around the world.
The concentration varies by location and by season (summer, winter) so as time passes, the line goes up and down.
On the right hand side of the screen we see a summary of this — how the average amount of CO2 in the atmosphere is changing over time. (Red line is in Hawaii. Blue line is at the South Pole.)
It is worth watching until the end.