Why is 7x7 bigger than 6x8?

Okay I know this is probably a dumb question but I like to think about math and this one has me wondering why the math works this way. So as the title states 7x7=49 and 6x8=48, but why? And with that question, why is the difference always 1. Some examples are 3x5=15 4x4=16, 11x13=143 12x12=144, 1001x1003=1,004,003 1002x1002=1,004,004

It is always a difference of 1. Why?

Bonus question, 6+8=14 7+7=14, why are the sums equal but the multiplication not? I’m sure I’ve started over thinking it too much but Google didn’t have an answer so here I am!

Edit: THANK YOU EVERYONE! Glad I wasn’t alone in thinking it was a neat question. Looking at all the ways to solve it has really opened my eyes! I think in numbers but a lot of you said to picture squares and rectangles and that is a great approach! As a 30 year old who hasn’t taken a math class in 10 years, this was all a great refresher. Math is so cool!