Early 90's I guess with bulletin boards but had heard about it earlier through use of home computers though.
For kids born after the mid 2000's they might not realise that anything other than text based pages used to take minutes to load a page right up until the turn of the century. It was a big deal getting a new modem that had jumped up in speed and you always knew someone who had paid out a fortune to get the latest one making you green with envy!
I still vividly remember when it started to become worth the pain of connecting and waiting for pages to load and for that you have to take into account for most of us with one phone line going online would knock out the use of the phone and seeing that was the hub of the home, people wouldn't be happy with you for it! I used to connect with AoL and use Yahoo as the search engine and I would say I was an early adopter of online shopping when people around me (mostly technical people - programmers and alike) were still very dubious about it all, I was already buying computers and monitors from Jungle.com.