The four pie charts show how old the people in Yemen and Italy were in 2000, and also how old they probably will be in 2050. Honestly, these two countries look almost like opposites, which makes it kind of interesting to compare.
In Yemen back in 2000, half of everybody was a kid under 15 (50.1%), and the working-age group from 15 to 59 was a bit smaller at 46.3%. Old people over 60 were really rare, only 3.6%. By 2050 the picture turns around a little. The kids drop to 37%, while the middle group jumps up to 57.3% and becomes the biggest piece. The elderly grow too, but only to 5.7%, so Yemen is still a pretty young country overall.
Italy is a totally different story. Already in 2000 only 14.3% were children, and the 15 to 59 group was the main one at 61.6%. Senior citizens were 24.1%, which is already way more than Yemen. Then in 2050 things get even more extreme. The over-60 group almost doubles to 42.3%, nearly catching up with the working people at 46.2%, and children shrink again to just 11.5%.
So basically, Yemen is slowly getting a bit older, but Italy is getting old much faster, and in the future it will have way more grandparents than kids.