In 1909, Nicola Tesla described what eventually would be a smartphone. They’ve existed in various forms for many years.
IBM invented a phone called the Angler in 1992 with PDA like functions. Subsequently, they released a commercial version in 1994.
The term “smartphone” first appears in 1995 describing AT&T’s PhoneWriter Communicator.
Eventually, more phones appeared in the US using Palm OS, Newton OS, Symbian, and Windows CE. Common functions included email, texting, calendar operations, really slow web browsing, and voice calls. Overall, they were slow and clunky.
HP and Nokia released a hybrid phone/PDA in 1996. It opened like a clamshell and contained a screen and keyboard.
In 1999, the Japanese firm NTT DoCoMo released the iMode, the first smartphone to gain mass adoption. Equally important, DoCoMo invented their own HTML-lite page description language, being the first to recognize the importance of high-quality content for smartphones.
Progress continued leading to the Handspring Treo that fully integrated a Palm Pilot and phone, in 2002.
In the early aughts, various phones typically had small physical keyboards, mimicking the then-popular Blackberry email/phone combination.
Subsequently, in 2007, Apple released the first iPhone. Initially, there were no apps nor app store: the iPhone did a small number of things and did them well. It was a web browser, email reader, texting device and phone. Sales were strong but not spectacular.
Hackers digitally broke into the iPhone enabling the installation of third-party apps. These became popular. Apple resisted at first but eventually created a process to install third-party apps without hacking and the iPhone app store opened in July 2008.
Android phones, based on an open-source operating system Google purchased, were released in October 2008.
Since then smartphones have become ubiquitous, dominated by Android (Google OS) and Apple. IBM and AT&T, developers of the earliest smartphones, do not produce smartphones.