Go to Yahoo! finance/financial glossary which will explain most of the terms
Try googling on each thing you want explained and you'll get plenty of info.
Hi Chloe,
An 'investment firm' can be a stockbroker, a wealth manager or institutional. As a beginner, the easiest place to start to begin to understand the is shares. A fund is simply a collection of shares, designed to eliminate risk by not relying on the performance of just one share. Link provides more info on why people invest in shares.
What's an investment firm? Shares, growth, mutual/closed end funds, stock funds, etc etc. I'm 15, so please make it easy to understand! Thank you.