In the iPod 1st, there were no keys for navigation. instead, there was a scroll wheel at the bottom of the screen.
After the success of ipod 1st, 2nd was released. then in 2003 ipod 3 was released with touch sensitive scrolling option. making it a touch enabled ipod. ipod 3 also supported dock charging and came with plethora of storage options at that time.
In 2005 they released 1st iPod shuffle which was having only 512MB of storage onboard & in 2006 with 1GB and 2GB storage options. iPod shuffle was a screenless, digital music player.
iPod shuffle instantly became the go-to device for gym enthusiasts, runners and teenagers all around the globe. it was an instant success for the shuffle.
iPod Nano was also released back in 2005 with many new features and issues. But in 2009 the fifth generation of the nano series did something amazing. it had a video camera inbuilt. which made the iPod nano to be the first iPod with camera functionality.
2009 iPod nano had many functions as the big screen, Fm radio, speaker and pedometer. it also came in lots of storage options with a limited 4GB edition as well.
Basically, the iPod touch is an iPhone without a sim tray. It can do all the other stuff like browsing the internet and watching videos. the first iPod touch was released back in 2007 and the 7th generation of the touch was released in 2019.