hi!! well there are some differences.. first.. Forex means foreign exchange so you tree world currencies!
shares... is stock market... such as apple, IBM, Microsoft, Google... and a lot more!!
the advantage about forex market is that you can use leverage... and you can get brokers that only get the spread (difference between bid and ask price)... on shares or stocks.. brokers charge you a fee for every movement you make...
you can absolutely start a career in online trading! and depending on your broker you can trade everything, currencies, commodities, indexes, shares, treasury bonds...
but the BEST thing you can do is see trading as you are doing it!! as a career!! and not as be rich in a day business because DISCIPLINE and RISK MANAGEMENT are the key to trading SUCCESS!